ezel 0.0.1

A good plotting library
Documentation 
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use super::linspace;

/// the length of a returned vec is around n.
pub fn heckbert(range: std::ops::Range<f64>, n: usize) -> Vec<f64> {
    let d = nice_numbers(range.end - range.start, false);
    let step = nice_numbers(d / (n - 1) as f64, true);
    let min = (range.start / step).floor() * step;
    let max = (range.end / step).ceil() * step;

    linspace(min..max, step)
}

/// x > 0
fn nice_numbers(x: f64, round: bool) -> f64 {
    let e = x.log10().floor();
    let ee = f64::powf(10.0, e);
    let f = x / ee;

    let nf = if round {
        match f {
            _ if f < 1.5 => 1.0,
            _ if f < 3.0 => 2.0,
            _ if f < 7.0 => 5.0,
            _ => 10.0,
        }
    } else {
        match f {
            _ if f <= 1.0 => 1.0,
            _ if f <= 2.0 => 2.0,
            _ if f <= 5.0 => 5.0,
            _ => 10.0,
        }
    };

    nf * ee
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn it_works() {
        assert_eq!(nice_numbers(1.2, false), 2.0);
        assert_eq!(nice_numbers(10.2, false), 20.0);
        assert_eq!(nice_numbers(7.36, false), 10.0);
        assert_eq!(
            heckbert(-4.19..3.761, 5),
            vec![-6.0, -4.0, -2.0, 0.0, 2.0, 4.0]
        );
        assert_eq!(heckbert(-4.19..3.761, 4), vec![-5.0, 0.0, 5.0]);
        assert_eq!(heckbert(8.1..14.1, 4), vec![5.0, 10.0, 15.0]);
    }
}