# `xan`, the CSV magician
`xan` is a command line tool that can be used to process CSV files directly from the shell.
It has been written in Rust to be as performant as possible and can easily handle very large CSV files (Gigabytes). It is also able to leverage parallelism (through multithreading) to make some tasks complete as fast as your computer can allow.
It can easily preview, filter, slice, aggregate, sort, join CSV files, and exposes a large collection of composable commands that can be chained together to perform a wide variety of typical tasks.
`xan` also leverages its own expression language so you can perform complex tasks that cannot be done by relying on the simplest commands. This minimalistic language has been tailored for CSV data and is faster than evaluating typical dynamically-typed languages such as Python, Lua, JavaScript etc.
Note that this tool is originally a fork of [BurntSushi](https://github.com/BurntSushi)'s [`xsv`](https://github.com/BurntSushi/xsv), but has been nearly entirely rewritten at that point, to fit [SciencesPo's médialab](https://github.com/medialab) use-cases, rooted in web data collection and analysis geared towards social sciences (you might think CSV is outdated by now, but read our [love letter](./docs/LOVE_LETTER.md) to the format before judging too quickly).
Finally, `xan` can be used to display CSV files in the terminal, for easy exploration, and can even be used to draw basic data visualisations.
*Displaying a CSV file in the terminal using `xan view`*
*Showing a flattened view of CSV records using `xan flatten`*
*Drawing a histogram of values using `xan hist`*
<p align="center">
<img alt="hist.png" src="./docs/img/hist.png" height="100">
</p>
*Drawing a scatterplot using `xan plot`*
<p align="center">
<img alt="scatter.png" src="./docs/img/scatter.png" height="400">
</p>
*Drawing a time series using `xan plot`*
<p align="center">
<img alt="line.png" src="./docs/img/line.png" height="300">
</p>
*Displaying a progress bar using `xan progress`*
<p align="center">
<img alt="progress.gif" src="./docs/img/progress.gif" width="90%">
</p>
## Summary
* [How to install](#how-to-install)
* [Quick tour](#quick-tour)
* [Available commands](#available-commands)
* [General flags and IO model](#general-flags-and-io-model)
* [Expression language reference](#expression-language-reference)
* [Syntax](#syntax)
* [Functions & Operators](#functions--operators)
* [Aggregation functions](#aggregation-functions)
* [Advanced use-cases](#advanced-use-cases)
* [Frequently Asked Questions](#frequently-asked-questions)
## How to install
`xan` can be installed using cargo (it usually comes with [Rust](https://www.rust-lang.org/tools/install)):
```
cargo install xan
```
## Quick tour
Let's learn about the most commonly used `xan` commands by exploring a corpus of French medias:
### Downloading the corpus
```bash
curl -LO https://github.com/medialab/corpora/raw/master/polarisation/medias.csv
```
### Displaying the file's headers
```bash
xan headers medias.csv
```
```
0 webentity_id
1 name
2 prefixes
3 home_page
4 start_pages
5 indegree
6 hyphe_creation_timestamp
7 hyphe_last_modification_timestamp
8 outreach
9 foundation_year
10 batch
11 edito
12 parody
13 origin
14 digital_native
15 mediacloud_ids
16 wheel_category
17 wheel_subcategory
18 has_paywall
19 inactive
```
### Counting the number of rows
```bash
xan count medias.csv
```
```
478
```
### Previewing the file in the terminal
```bash
xan view medias.csv
```
```
Displaying 5/20 cols from 10 first rows of medias.csv
┌───┬───────────────┬───────────────┬────────────┬───┬─────────────┬──────────┐
│ - │ name │ prefixes │ home_page │ … │ has_paywall │ inactive │
├───┼───────────────┼───────────────┼────────────┼───┼─────────────┼──────────┤
│ 0 │ Acrimed.org │ http://acrim… │ http://ww… │ … │ false │ <empty> │
│ 1 │ 24matins.fr │ http://24mat… │ https://w… │ … │ false │ <empty> │
│ 2 │ Actumag.info │ http://actum… │ https://a… │ … │ false │ <empty> │
│ 3 │ 2012un-Nouve… │ http://2012u… │ http://ww… │ … │ false │ <empty> │
│ 4 │ 24heuresactu… │ http://24heu… │ http://24… │ … │ false │ <empty> │
│ 5 │ AgoraVox │ http://agora… │ http://ww… │ … │ false │ <empty> │
│ 6 │ Al-Kanz.org │ http://al-ka… │ https://w… │ … │ false │ <empty> │
│ 7 │ Alalumieredu… │ http://alalu… │ http://al… │ … │ false │ <empty> │
│ 8 │ Allodocteurs… │ http://allod… │ https://w… │ … │ false │ <empty> │
│ 9 │ Alterinfo.net │ http://alter… │ http://ww… │ … │ <empty> │ true │
│ … │ … │ … │ … │ … │ … │ … │
└───┴───────────────┴───────────────┴────────────┴───┴─────────────┴──────────┘
```
On unix, don't hesitate to use the `-p` flag to automagically forward the full output to an appropriate pager and skim through all the columns.
### Reading a flattened representation of the first row
```bash
# NOTE: drop -c to avoid truncating the values
```
Row n°0
───────────────────────────────────────────────────────────────────────────────
webentity_id 1
name Acrimed.org
start_pages http://acrimed.org|http://acrimed69.blogspot…
indegree 61
hyphe_creation_timestamp 1560347020330
hyphe_last_modification_timestamp 1560526005389
outreach nationale
foundation_year 2002
batch 1
edito media
parody false
origin france
digital_native true
mediacloud_ids 258269
wheel_category Opinion Journalism
wheel_subcategory Left Wing
has_paywall false
inactive <empty>
```
### Searching for rows
```bash
```
Displaying 4/20 cols from 10 first rows of <stdin>
┌───┬──────────────┬────────────────────┬───┬─────────────┬──────────┐
│ - │ webentity_id │ name │ … │ has_paywall │ inactive │
├───┼──────────────┼────────────────────┼───┼─────────────┼──────────┤
│ 0 │ 25 │ Businessinsider.fr │ … │ false │ <empty> │
│ 1 │ 59 │ Europe-Israel.org │ … │ false │ <empty> │
│ 2 │ 66 │ France 24 │ … │ false │ <empty> │
│ 3 │ 220 │ RFI │ … │ false │ <empty> │
│ 4 │ 231 │ fr.Sott.net │ … │ false │ <empty> │
│ 5 │ 246 │ Voltairenet.org │ … │ true │ <empty> │
│ 6 │ 254 │ Afp.com /fr │ … │ false │ <empty> │
│ 7 │ 265 │ Euronews FR │ … │ false │ <empty> │
│ 8 │ 333 │ Arte.tv │ … │ false │ <empty> │
│ 9 │ 341 │ I24News.tv │ … │ false │ <empty> │
│ … │ … │ … │ … │ … │ … │
└───┴──────────────┴────────────────────┴───┴─────────────┴──────────┘
```
### Selecting some columns
```bash
xan select foundation_year,name medias.csv | xan view
```
```
Displaying 2 cols from 10 first rows of <stdin>
┌───┬─────────────────┬───────────────────────────────────────┐
│ - │ foundation_year │ name │
├───┼─────────────────┼───────────────────────────────────────┤
│ 0 │ 2002 │ Acrimed.org │
│ 1 │ 2006 │ 24matins.fr │
│ 2 │ 2013 │ Actumag.info │
│ 3 │ 2012 │ 2012un-Nouveau-Paradigme.com │
│ 4 │ 2010 │ 24heuresactu.com │
│ 5 │ 2005 │ AgoraVox │
│ 6 │ 2008 │ Al-Kanz.org │
│ 7 │ 2012 │ Alalumieredunouveaumonde.blogspot.com │
│ 8 │ 2005 │ Allodocteurs.fr │
│ 9 │ 2005 │ Alterinfo.net │
│ … │ … │ … │
└───┴─────────────────┴───────────────────────────────────────┘
```
### Sorting the file
```bash
```
Displaying 2 cols from 10 first rows of <stdin>
┌───┬────────────────────────────────────┬─────────────────┐
│ - │ name │ foundation_year │
├───┼────────────────────────────────────┼─────────────────┤
│ 0 │ Le Monde Numérique (Ouest France) │ <empty> │
│ 1 │ Le Figaro │ 1826 │
│ 2 │ Le journal de Saône-et-Loire │ 1826 │
│ 3 │ L'Indépendant │ 1846 │
│ 4 │ Le Progrès │ 1859 │
│ 5 │ La Dépêche du Midi │ 1870 │
│ 6 │ Le Pélerin │ 1873 │
│ 7 │ Dernières Nouvelles d'Alsace (DNA) │ 1877 │
│ 8 │ La Croix │ 1883 │
│ 9 │ Le Chasseur Francais │ 1885 │
│ … │ … │ … │
└───┴────────────────────────────────────┴─────────────────┘
```
### Deduplicating the file on some column
```bash
# Some medias of our corpus have the same ids on mediacloud.org
xan dedup -s mediacloud_ids medias.csv | xan count && xan count medias.csv
```
```
457
478
```
Deduplicating can also be done while sorting:
```bash
xan sort -s mediacloud_ids -u medias.csv
```
### Computing frequency tables
```bash
```
Displaying 3 cols from 5 rows of <stdin>
┌───┬───────┬────────────┬───────┐
│ - │ field │ value │ count │
├───┼───────┼────────────┼───────┤
│ 0 │ edito │ media │ 423 │
│ 1 │ edito │ individu │ 30 │
│ 2 │ edito │ plateforme │ 14 │
│ 3 │ edito │ agrégateur │ 10 │
│ 4 │ edito │ agence │ 1 │
└───┴───────┴────────────┴───────┘
```
### Printing a histogram
```bash
```
Histogram for edito (bars: 5, sum: 478, max: 423):
plateforme | 14 2.93%|━╸ |
agrégateur | 10 2.09%|━╸ |
agence | 1 0.21%|╸ |
```
### Computing descriptive statistics
```bash
```
Displaying 2 cols from 14 rows of <stdin>
┌─────────────┬───────────────────┬────────────┐
│ field │ indegree │ edito │
├─────────────┼───────────────────┼────────────┤
│ count │ 463 │ 478 │
│ count_empty │ 15 │ 0 │
│ type │ int │ string │
│ mean │ 56.12742980561554 │ <empty> │
│ variance │ 4234.530197929737 │ <empty> │
│ stddev │ 65.07326792108829 │ <empty> │
│ min │ 0 │ <empty> │
│ max │ 424 │ <empty> │
│ lex_first │ 0 │ agence │
│ lex_last │ 99 │ plateforme │
│ min_length │ 0 │ 5 │
│ max_length │ 3 │ 11 │
└─────────────┴───────────────────┴────────────┘
```
### Evaluating an expression to filter a file
```bash
```
130
```
To access the expression language's [cheatsheet](#syntax), run `xan filter --cheatsheet`. To display the full list of available [functions](#functions--operators), run `xan filter --functions`.
### Evaluating an expression to create a new column based on other ones
```bash
xan map 'fmt("{} ({})", name, foundation_year)' key medias.csv | xan select key | xan slice -l 10
```
```
key
Acrimed.org (2002)
24matins.fr (2006)
Actumag.info (2013)
2012un-Nouveau-Paradigme.com (2012)
24heuresactu.com (2010)
AgoraVox (2005)
Al-Kanz.org (2008)
Alalumieredunouveaumonde.blogspot.com (2012)
Allodocteurs.fr (2005)
Alterinfo.net (2005)
```
To access the expression language's [cheatsheet](#syntax), run `xan map --cheatsheet`. To display the full list of available [functions](#functions--operators), run `xan map --functions`.
### Transform a column by evaluating an expression
```bash
```
name
ACRIMED
24MATINS
ACTUMAG
2012UN-NOUVEAU-PARADIGME
24HEURESACTU
AGORAVOX
AL-KANZ
ALALUMIEREDUNOUVEAUMONDE
ALLODOCTEURS
ALTERINFO
```
To access the expression language's [cheatsheet](#syntax), run `xan transform --cheatsheet`. To display the full list of available [functions](#functions--operators), run `xan transform --functions`.
### Performing custom aggregation
```bash
```
Displaying 1 col from 1 rows of <stdin>
┌────────────────┬───────────────────┐
│ total_indegree │ mean_indegree │
├────────────────┼───────────────────┤
│ 25987 │ 56.12742980561554 │
└────────────────┴───────────────────┘
```
To access the expression language's [cheatsheet](#syntax), run `xan agg --cheatsheet`. To display the full list of available [functions](#functions--operators), run `xan agg --functions`. Finally, to display the list of available [aggregation functions](#aggregation-functions), run `xan agg --aggs`.
### Grouping rows and performing per-group aggregation
```bash
```
Displaying 1 col from 5 rows of <stdin>
┌────────────┬──────────┐
│ edito │ indegree │
├────────────┼──────────┤
│ agence │ 50 │
│ agrégateur │ 459 │
│ plateforme │ 658 │
│ media │ 24161 │
│ individu │ 659 │
└────────────┴──────────┘
```
To access the expression language's [cheatsheet](#syntax), run `xan groupby --cheatsheet`. To display the full list of available [functions](#functions--operators), run `xan groupby --functions`. Finally, to display the list of available [aggregation functions](#aggregation-functions), run `xan groupby --aggs`.
## Available commands
*All commands are not fully documented on this README yet, but all the necessary information can be found directly from the command line. Just run `xan command -h` for help*
- **agg** - Aggregate data from CSV file
- [**behead**](./docs/cmd/behead.md) - Drop header from CSV file
- **bins** - Dispatch numeric columns into bins
- **blank** - Blank down a CSV file
- **cat** - Concatenate by row or column
- **cluster** - Cluster CSV data to find near-duplicates
- [**count**](./docs/cmd/count.md) - Count records
- **dedup** - Deduplicate a CSV file
- **enum** - Enumerate CSV file by preprending an index column
- **explode** - Explode rows based on some column separator
- **filter** - Only keep some CSV rows based on an evaluated expression
- **fixlengths** - Makes all records have same length
- **flatmap** - Emit one row per value yielded by an expression evaluated for each CSV row
- **flatten** - Show one field per line
- **fmt** - Format CSV output (change field delimiter)
- **foreach** - Loop over a CSV file to perform side effects
- **frequency** - Show frequency tables
- **from** - Convert a variety of formats to CSV
- **glob** - Create a CSV file with paths matching a glob pattern
- **groupby** - Aggregate data by groups of a CSV file
- [**headers**](./docs/cmd/headers.md) - Show header names
- **hist** - Print a histogram with rows of CSV file as bars
- **implode** - Collapse consecutive identical rows based on a diverging column
- **index** - Create CSV index for faster access
- **input** - Read CSV data with special quoting rules
- **join** - Join CSV files
- **map** - Create a new column by evaluating an expression on each CSV row
- **merge** - Merge multiple similar already sorted CSV files
- **partition** - Partition CSV data based on a column value
- **plot** - Draw a scatter plot or line chart
- **progress** - Display a progress bar while reading CSV data
- **range** - Create a CSV file from a numerical range
- **rename** - Rename columns of a CSV file
- **reverse** - Reverse rows of CSV data
- **sample** - Randomly sample CSV data
- **search** - Search CSV data with regexes
- **select** - Select columns from CSV
- **shuffle** - Shuffle CSV data
- **slice** - Slice records from CSV
- **sort** - Sort CSV data
- **split** - Split CSV data into many files
- **stats** - Compute basic statistics
- **tokenize** - Tokenize a text column
- **top** - Find top rows of a CSV file according to some column
- **transform** - Transform a column by evaluating an expression on each CSV row
- **transpose** - Transpose CSV file
- **union-find** - Apply the union-find algorithm on a CSV edge list
- **view** - Preview a CSV file in a human-friendly way
- **vocab** - Build a vocabulary over tokenized documents
## General flags and IO model
### Getting help
If you ever feel lost, each command has a `-h/--help` flag that will print the related documentation.
### Regarding input & output formats
All `xan` commands expect a "standard" CSV file, e.g. comma-delimited, with proper double-quote escaping. This said, `xan` is also perfectly able to infer the delimiter from typical file extensions such as `.tsv` or `.tab`.
If you need to process a file with a custom delimiter, you can either use the `xan input` command or use the `-d/--delimiter` flag available with all commands.
If you need to output a custom CSV dialect (e.g. using `;` delimiters), feel free to use the `xan fmt` command.
Finally, even if most `xan` commands won't even need to decode the file's bytes, some might still need to. In this case, `xan` will expect correctly formatted UTF-8 text. Please use `iconv` or other utils if you need to process other encodings such as `latin1` ahead of `xan`.
### Working with headless CSV file
Even if this is good practice to name your columns, some CSV file simply don't have headers. Most commands are able to deal with those file if you give the `-n/--no-headers` flag.
Note that this flag always relates to the input, not the output. If for some reason you want to drop a CSV output's header row, use the `xan behead` command.
### Regarding stdin
By default, all commands will try to read from stdin when the file path is not specified. This makes piping easy and comfortable as it respects typical unix standards. Some commands may have multiple inputs (`xan join`, for instance), in which case stdin is usually specifiable using the `-` character:
```bash
# First file given to join will be read from stdin
Note that the command will also warn you when stdin cannot be read, in case you forgot to indicate the file's path.
### Regarding stdout
By default, all commands will print their output to stdout (note that this output is usually buffered for performance reasons).
In addition, all commands expose a `-o/--output` flag that can be use to specify where to write the output. This can be useful if you do not want to or cannot use `>` (typically in some Windows shells). In which case, `-` as a output path will mean forwarding to stdout also. This can be useful when scripting sometimes.
### Gzipped files
`xan` is able to read gzipped files (having a `.gz` extension) out of the box.
## Expression language reference
### Syntax
This help can be found in the terminal by executing `xan map --cheatsheet`.
```
xan script language cheatsheet (use --functions for comprehensive list of
available functions & operators):
. Indexing a column by name:
'name'
. Indexing column with forbidden characters (e.g. spaces, commas etc.):
'col("Name of film")'
. Indexing column by index (0-based):
'col(2)'
. Indexing a column by name and 0-based nth (for duplicate headers):
'col("col", 1)'
. Applying functions:
'trim(name)'
'trim(concat(name, " ", surname))'
. Named function arguments:
'read(path, encoding="utf-8")'
. Using operators (unary & binary):
'-nb1'
'nb1 + nb2'
'(nb1 > 1) || nb2'
. Integer literals:
'1'
. Float literals:
'0.5'
. Boolean literals:
'true'
'false'
. Null literals:
'null'
. String literals (can use single or double quotes):
'"hello"'
"'hello'"
. Regex literals:
'/john/'
'/john/i' (case-insensitive)
. List literals:
'[1, 2, 3]'
'["one", "two"]
. Map literals:
'{one: 1, two: 2}'
'{leaf: "hello", "nested": [1, 2, 3]}'
Note that constant expressions will never be evaluated more than once
when parsing the program.
This means that when evaluating the following:
'get(read_json("config.json"), name)'
The "config.json" file will never be read/parsed more than once and will not
be read/parsed once per row.
```
### Functions & Operators
This help can be found in the terminal by executing `xan map --functions`.
```
# Available functions & operators
(use --cheatsheet for a reminder of the expression language's basics)
## Operators
### Unary operators
!x - boolean negation
-x - numerical negation,
### Numerical comparison
Warning: those operators will always consider operands as numbers and will
try to cast them around as such. For string/sequence comparison, use the
operators in the next section.
x == y - numerical equality
x != y - numerical inequality
x < y - numerical less than
x <= y - numerical less than or equal
x > y - numerical greater than
x >= y - numerical greater than or equal
### String/sequence comparison
Warning: those operators will always consider operands as strings or
sequences and will try to cast them around as such. For numerical comparison,
use the operators in the previous section.
x eq y - string equality
x ne y - string inequality
x lt y - string less than
x le y - string less than or equal
x gt y - string greater than
x ge y - string greater than or equal
### Arithmetic operators
x + y - numerical addition
x - y - numerical subtraction
x * y - numerical multiplication
x / y - numerical division
x % y - numerical remainder
x // y - numerical integer division
x ** y - numerical exponentiation
## String operators
x . y - string concatenation
## Logical operators
x && y - logical and
x and y
x || y - logical or
x or y
x in y
x not in y
## Indexing & slicing operators
x[y] - get y from x (string or list index, map key)
x[start:end] - slice x from start index to end index
x[:end] - slice x from start to end index
x[start:] - slice x from start index to end
Negative indices are accepted and mean the same thing as with
the Python language.
## Pipeline operator (using "_" for left-hand size substitution)
'trim(name) | len(_)' - Same as len(trim(name))
'trim(name) | len' - Supports elision for unary functions
'trim(name) | add(1, len(_))' - Can be nested
'add(trim(name) | len, 2)' - Can be used anywhere
## Arithmetics
- abs(x) -> number
Return absolute value of number.
- add(x, y, *n) -> number
Add two or more numbers.
- argmax(numbers, labels?) -> any
Return the index or label of the largest number in the list.
- argmin(numbers, labels?) -> any
Return the index or label of the smallest number in the list.
- ceil(x) -> number
Return the smallest integer greater than or equal to x.
- div(x, y, *n) -> number
Divide two or more numbers.
- floor(x) -> number
Return the smallest integer lower than or equal to x.
- idiv(x, y) -> number
Integer division of two numbers.
- log(x) -> number
Return the natural logarithm of x.
- max(x, y, *n) -> number
- max(list_of_numbers) -> number
Return the maximum number.
- min(x, y, *n) -> number
- min(list_of_numbers) -> number
Return the minimum number.
- mod(x, y) -> number
Return the remainder of x divided by y.
- mul(x, y, *n) -> number
Multiply two or more numbers.
- neg(x) -> number
Return -x.
- pow(x, y) -> number
Raise x to the power of y.
- round(x) -> number
Return x rounded to the nearest integer.
- sqrt(x) -> number
Return the square root of x.
- sub(x, y, *n) -> number
Subtract two or more numbers.
- trunc(x) -> number
Truncate the number by removing its decimal part.
## Boolean operations & branching
- and(a, b, *x) -> T
Perform boolean AND operation on two or more values.
- if(cond, then, else?) -> T
Evaluate condition and switch to correct branch.
- unless(cond, then, else?) -> T
Shorthand for `if(not(cond), then, else?)`.
- not(a) -> bool
Perform boolean NOT operation.
- or(a, b, *x) -> T
Perform boolean OR operation on two or more values.
## Comparison
- eq(s1, s2) -> bool
Test string or sequence equality.
- ne(s1, s2) -> bool
Test string or sequence inequality.
- gt(s1, s2) -> bool
Test that string or sequence s1 > s2.
- ge(s1, s2) -> bool
Test that string or sequence s1 >= s2.
- lt(s1, s2) -> bool
Test that string or sequence s1 < s2.
- ge(s1, s2) -> bool
Test that string or sequence s1 <= s2.
## String & sequence helpers
- compact(list) -> list
Drop all falsey values from given list.
- concat(string, *strings) -> string
Concatenate given strings into a single one.
- contains(seq, subseq) -> bool
Find if subseq can be found in seq. Subseq can
be a regular expression.
- count(seq, pattern) -> int
Count number of times pattern appear in seq. Pattern
can be a regular expression.
- endswith(string, pattern) -> bool
Test if string ends with pattern.
- escape_regex(string) -> string
Escape a string so it can be used safely in a regular expression.
- first(seq) -> T
Get first element of sequence.
- fmt(string, *replacements):
Format a string by replacing "{}" occurrences by subsequent
arguments.
Example: `fmt("Hello {} {}", name, surname)` will replace
the first "{}" by the value of the name column, then the
second one by the value of the surname column.
- get(target, index_or_key, default?) -> T
Get nth element of sequence (can use negative indexing), or key of mapping.
Returns nothing if index or key is not found or alternatively the provided
default value.
- join(seq, sep) -> string
Join sequence by separator.
- last(seq) -> T
Get last element of sequence.
- len(seq) -> int
Get length of sequence.
- ltrim(string, pattern?) -> string
Trim string of leading whitespace or
provided characters.
- lower(string) -> string
Lowercase string.
- match(string, pattern, group?) -> string
Return a regex pattern match on the string.
- replace(string, pattern, replacement) -> string
Replace pattern in string. Can use a regex.
- rtrim(string, pattern?) -> string
Trim string of trailing whitespace or
provided characters.
- slice(seq, start, end?) -> seq
Return slice of sequence.
- split(string, sep, max?) -> list
Split a string by separator.
- startswith(string, pattern) -> bool
Test if string starts with pattern.
- trim(string, pattern?) -> string
Trim string of leading & trailing whitespace or
provided characters.
- unidecode(string) -> string
Convert string to ascii as well as possible.
- upper(string) -> string
Uppercase string.
## Dates
- datetime(string, format=?, timezone=?) -> datetime
Parse a string as a datetime according to format and timezone
(https://docs.rs/jiff/latest/jiff/fmt/strtime/index.html#conversion-specifications).
If no format is provided, string is parsed as ISO 8601 date format.
Default timezone is the system timezone.
- strftime(target, format, timezone=?) -> string
Format target (a time in ISO 8601 format,
or the result of datetime() function) according to format.
- timestamp(number) -> datetime
Parse a number as a POSIX timestamp in seconds
(nb of seconds since 1970-01-01 00:00:00 UTC),
and convert it to a datetime in local time.
- timestamp_ms(number) -> datetime
Parse a number as a POSIX timestamp in milliseconds
(nb of milliseconds since 1970-01-01 00:00:00 UTC),
and convert it to a datetime in local time.
## Collections (list of maps) functions
- index_by(collection, key) -> map
Create a map from item key to collection item.
## Map functions
- keys(map) -> [string]
Return a list of the map's keys.
- values(map) -> [T]
Return a list of the map's values.
## List aggregation functions
- mean(numbers) -> number?
Return the means of the given numbers.
## Fuzzy matching
- fingerprint(string) -> string
Fingerprints a string by normalizing characters, re-ordering
and deduplicating its word tokens before re-joining them by
spaces.
## Utils
- coalesce(*args) -> T
Return first truthy value.
- col(name_or_pos, nth?) -> string
Return value of cell for given column, by name, by position or by
name & nth, in case of duplicate header names.
- cols(from_name_or_pos?, to_name_or_pos?) -> list
Return list of cell values from the given colum by name or position
to another given column by name or position, inclusive.
Can also be called with a single argument to take a slice from the
given column to the end, or no argument at all to take all columns.
- err(msg) -> error
Make the expression return a custom error.
- headers(from_name_or_pos?, to_name_or_pos?) -> list
Return list of header names from the given colum by name or position
to another given column by name or position, inclusive.
Can also be called with a single argument to take a slice from the
given column to the end, or no argument at all to return all headers.
- index() -> integer?
Return the row's index, if applicable.
- json_parse(string) -> any
Parse the given string as JSON.
- typeof(value) -> string
Return type of value.
## IO & path wrangling
- abspath(string) -> string
Return absolute & canonicalized path.
- bytesize(integer) -> string
Return a number of bytes in human-readable format (KB, MB, GB, etc.).
- copy(source_path, target_path) -> string
Copy a source to target path. Will create necessary directories
on the way. Returns target path as a convenience.
- ext(path) -> string?
Return the path's extension, if any.
- filesize(string) -> int
Return the size of given file in bytes.
- isfile(string) -> bool
Return whether the given path is an existing file on disk.
- move(source_path, target_path) -> string
Move a source to target path. Will create necessary directories
on the way. Returns target path as a convenience.
- pathjoin(string, *strings) -> string
Join multiple paths correctly.
- read(path, encoding=?, errors=?) -> string
Read file at path. Default encoding is "utf-8".
Default error handling policy is "replace", and can be
one of "replace", "ignore" or "strict".
- read_csv(path) -> list[map]
Read and parse CSV file at path, returning its rows as
a list of maps with headers as keys.
- read_json(path) -> any
Read and parse JSON file at path.
- write(string, path) -> string
Write string to path as utf-8 text. Will create necessary
directories recursively before actually writing the file.
Return the path that was written.
## Random
- md5(string) -> string
Return the md5 hash of string in hexadecimal representation.
- uuid() -> string
Return a uuid v4.
```
### Aggregation functions
This help can be found in the terminal by executing `xan agg --aggs`.
```
# Available aggregation functions
(use --cheatsheet for a reminder of how the scripting language works)
Note that most functions ignore null values (empty strings), but that functions
operating on numbers will yield an error if encountering a string that cannot
be safely parsed as a number.
You can always use `coalesce` to nudge values around and force aggregation functions to
consider null values or make them avoid non-numerical values altogether.
Example: considering null values when computing a mean => 'mean(coalesce(number, 0))'
- all(<expr>) -> bool
Returns true if all elements returned by given expression are truthy.
- any(<expr>) -> bool
Returns true if one of the elements returned by given expression is truthy.
- argmin(<expr>, <expr>?) -> any
Return the index of the row where the first expression is minimized, or
the result of the second expression where the first expression is minimized.
Ties will be broken by original row index.
- argmax(<expr>, <expr>?) -> any
Return the index of the row where the first expression is maximized, or
the result of the second expression where the first expression is maximized.
Ties will be broken by original row index.
- argtop(k, <expr>, <expr>?, separator?)
Find the top k values returned by the first expression and either
return the indices of matching rows or the result of the second
expression, joined by a pipe character ('|') or by the provided separator.
Ties will be broken by original row index.
- avg(<expr>) -> number
Average of numerical values. Same as `mean`.
- cardinality(<expr>) -> number
Number of distinct values returned by given expression.
- count(<expr>?) -> number
Count the number of row. Works like in SQL in that `count(<expr>)`
will count all non-empy values returned by given expression, while
`count()` without any expression will count every matching row.
- count_empty(<expr>) -> number
Count the number of empty values returned by given expression.
- distinct_values(<expr>, separator?) -> string
List of sorted distinct values joined by a pipe character ('|') by default or by
the provided separator.
- first(<expr>) -> string
Return first seen non empty element of the values returned by the given expression.
- last(<expr>) -> string
Return last seen non empty element of the values returned by the given expression.
- lex_first(<expr>) -> string
Return first string in lexicographical order.
- lex_last(<expr>) -> string
Return last string in lexicographical order.
- min(<expr>) -> number | string
Minimum numerical value.
- max(<expr>) -> number | string
Maximum numerical value.
- mean(<expr>) -> number
Mean of numerical values. Same as `avg`.
- median(<expr>) -> number
Median of numerical values, interpolating on even counts.
- median_high(<expr>) -> number
Median of numerical values, returning higher value on even counts.
- median_low(<expr>) -> number
Median of numerical values, returning lower value on even counts.
- mode(<expr>) -> string
Value appearing the most, breaking ties arbitrarily in favor of the
first value in lexicographical order.
- most_common(k, <expr>, separator?)
List of top k most common values returned by expression
joined by a pipe character ('|') or by the provided separator.
Ties will be broken by lexicographical order.
- most_common_counts(k, <expr>, separator?)
List of top k most common counts returned by expression
joined by a pipe character ('|') or by the provided separator.
- quantile(<expr>, p) -> number
Return the desired quantile of numerical values.
- q1(<expr>) -> number
Return the first quartile of numerical values.
- q2(<expr>) -> number
Return the second quartile of numerical values. Alias for median.
- q3(<expr>) -> number
Return the third quartile of numerical values.
- stddev(<expr>) -> number
Population standard deviation. Same as `stddev_pop`.
- stddev_pop(<expr>) -> number
Population standard deviation. Same as `stddev`.
- stddev_sample(<expr>) -> number
Sample standard deviation (i.e. using Bessel's correction).
- sum(<expr>) -> number
Sum of numerical values.
- top(k, <expr>, separator?)
Find the top k values returned by the expression and join
them by a pipe character ('|') or by the provided separator.
Ties will be broken by original row index.
- type(<expr>) -> string
Best type description for seen values.
- types(<expr>) -> string
Sorted list, pipe-separated, of all the types seen in the values.
- values(<expr>, separator?) -> string
List of values joined by a pipe character ('|') by default or by
the provided separator.
- var(<expr>) -> number
Population variance. Same as `var_pop`.
- var_pop(<expr>) -> number
Population variance. Same as `var`.
- var_sample(<expr>) -> number
Sample variance (i.e. using Bessel's correction).
```
## Advanced use-cases
### Reading files in parallel
Let's say one column of your CSV file is containing paths to files, relative to some `downloaded` folder, and you want to make sure all of them contain some string (maybe you crawled some website and want to make sure you were correctly logged in by searching for some occurrence of your username):
```bash
```
### Generating a CSV of paginated urls to download
Let's say you want to download the latest 50 pages from [Hacker News](https://news.ycombinator.com) using another of our tools named [minet](https://github.com/medialab/minet).
You can pipe `xan range` into `xan select -e` into `minet fetch`:
```bash
minet fetch url -i -
```
### Piping to `xargs`
Let's say you want to delete all files whose path can be found in a column of CSV file. You can select said column and format it with `xan` before piping to `xargs`:
```bash
xan fmt --quote-never | \
xargs -I {} rm {};
```
## Frequently Asked Questions
### How to display a vertical bar chart?
Rotate your screen ;\)