timelag — creating time lagged data series

This crate provides lag_matrix and related functions to create time-lagged versions of time series.

```rust use timelag::lag_matrix;

fn it_works() { let data = [1.0, 2.0, 3.0, 4.0];

// Using infinity for padding because NaN doesn't equal itself.
let lag = f64::INFINITY;
let padding = f64::INFINITY;

let direct = lag_matrix(&data, 3, lag, 5).unwrap();

assert_eq!(
    direct,
    &[
        1.0, 2.0, 3.0, 4.0, padding, // original data
        lag, 1.0, 2.0, 3.0, padding, // first lag
        lag, lag, 1.0, 2.0, padding, // second lag
        lag, lag, lag, 1.0, padding, // third lag
    ]
);

} ```