Module graph 

Customizable graphing calculator.

This module provides basic graphing functionality, such as plotting expressions and points, then rendering the result to an image.

To build an image of a graph, create a Graph and add expressions and / or points to it using Graph::add_expr / Graph::try_add_expr and Graph::add_point. Then, call Graph::draw() to render the graph to an image. This crate uses the cairo crate to render the graph, and thus can render to any format supported by cairo, including PNG and SVG.

Adding expressions

The argument to Graph::try_add_expr() is any expression that can be parsed by cas_parser as an Expr. If you have an Expr already, you can use Graph::add_expr().

The given expression should be one defined in terms of the variables x (horizontal axis), y (vertical axis), or both, with an optional y == or x == prefix / suffix to clearly indicate the dependent variable. For example, the following are all valid expressions:

• y == 0.8214285714x^2 + 4.3785714286x + 7
• 0.8214285714x^2 + 4.3785714286x + 7
• sin(x) == y
• sin(y)
• x == sin(y)
• x^2 + y^2 == 1 TODO: relations are not yet supported
• etc.

Customizing visuals

The graph can be configured by passing a custom GraphOptions to Graph::with_opts to customize the viewport size, scale, and grid divisions. See GraphOptions for a description of each option along with their defaults.

Example

The following example creates a graph with the expression y == 0.8214285714x^2 + 4.3785714286x + 7 and a few points with the viewport centered on the added points. The graph is then rendered to a PNG file.

use cas_graph::{Graph, GraphOptions};
use std::fs::File;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let opts = GraphOptions::default()
        .square_scale(true); // scales the x- and y-axes together, looks nicer in my opinion
    let surface = Graph::with_opts(opts)
        .try_add_expr("y == 0.8214285714x^2 + 4.3785714286x + 7").unwrap()
    //  .try_add_expr("0.8214285714x^2 + 4.3785714286x + 7").unwrap() // "y==" can be omitted
        .add_point((-5.0, 5.0))
        .add_point((-4.0, 4.0))
        .add_point((-3.0, 1.0))
        .add_point((-2.0, 0.5))
        .add_point((-1.0, 4.0))
        .center_on_points()
        .draw()?;

    let mut file = File::create("output.png")?;
    surface.write_to_png(&mut file)?;

    Ok(())
}

Output (note: colors were randomly chosen; random color selection is not included in the example code):

Re-exports

pub use point::CanvasPoint;

pub use point::GraphPoint;

pub use point::Point;

pub use opts::GraphOptions;

Modules

analyzed

opts

point

Structs

Graph

A graph containing expressions and points to draw.