Function ma_diff 

pub fn ma_diff(
    a: &MaskedArray<f64, IxDyn>,
    n: usize,
    axis: isize,
) -> FerrayResult<MaskedArray<f64, IxDyn>>

numpy.ma.diff(a, n=1, axis=-1) — the n-th discrete difference along axis, preserving the mask (numpy/ma/core.py:7774).

out[i] = a[i+1] - a[i]; a result position is masked iff either of the two operands feeding it is masked. For n > 1 the difference is applied recursively (each pass shrinks axis by 1). n == 0 returns a unchanged. axis is the usual signed axis (-1 = last).

Errors

Returns FerrayError::InvalidValue for a 0-D input, AxisOutOfBounds for an out-of-range axis, or an internal error.