gamlss_transform/transforms/
log.rs

1use crate::{TargetTransform, TransformError, map_slice_into, validate_positive};
2
3/// Log transform for strictly positive targets.
4#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
5pub struct Log;
6
7/// State for [`Log`].
8#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
9pub struct LogState;
10
11impl TargetTransform for Log {
12    type State = LogState;
13
14    fn fit(y: &[f64]) -> Result<Self::State, TransformError> {
15        validate_positive(y)?;
16        Ok(LogState)
17    }
18
19    fn transform(_: &Self::State, y: f64) -> f64 {
20        y.ln()
21    }
22
23    fn inverse(_: &Self::State, value: f64) -> f64 {
24        value.exp()
25    }
26
27    fn transform_slice(state: &Self::State, y: &[f64]) -> Result<Vec<f64>, TransformError> {
28        let mut out = vec![0.0; y.len()];
29        Self::transform_into(state, y, &mut out)?;
30        Ok(out)
31    }
32
33    fn transform_into(
34        state: &Self::State,
35        y: &[f64],
36        out: &mut [f64],
37    ) -> Result<(), TransformError> {
38        map_slice_into(y, out, validate_positive, |value| {
39            Self::transform(state, value)
40        })
41    }
42}
43
44#[cfg(test)]
45mod tests {
46    use approx::assert_relative_eq;
47
48    use crate::{Log, TargetTransform, TransformError};
49
50    #[test]
51    fn round_trips_positive_values() {
52        let y = [1.0, 2.5];
53        let (state, transformed) = Log::fit_transform(&y).unwrap();
54        let restored = Log::inverse_slice(&state, &transformed).unwrap();
55
56        for (actual, expected) in restored.iter().zip(y) {
57            assert_relative_eq!(*actual, expected);
58        }
59    }
60
61    #[test]
62    fn rejects_invalid_domain() {
63        assert_eq!(
64            Log::fit(&[1.0, 0.0]).unwrap_err(),
65            TransformError::NonPositiveValue
66        );
67        assert_eq!(
68            Log::fit(&[f64::INFINITY]).unwrap_err(),
69            TransformError::NonFiniteValue
70        );
71    }
72}
gamlss_transform/transforms/log.rs

gamlss_transform/transforms/
log.rs
