[RFC]: add `stats/strided/zscore`

[kgryte]

This API implements

$$y = \frac{x - \overline{x}}{\sigma_x}$$

This API computes the z-score.

API signatures:

zscore( N, correction, x, strideX, y, strideY )
zscore.ndarray( N, correction, x, strideX, offsetX, y, strideY, offsetY )

where

• N: number of indexed elements.
• correction: degrees of freedom adjustment.
• x: input strided array.
• strideX: stride length for x.
• offsetX: starting index for x.
• y: output strided array.
• strideY: stride length for y.
• offsetY: starting index for y.

Notes

• Should be able to use stats/strided/meanstdev to compute the mean and stdev in a single pass and then call blas/ext/base/*xsadb.

Follow-on Work

Once completed and merged, the following packages can be added

• [RFC]: add stats/strided/dzscore
• [RFC]: add stats/strided/szscore
• [RFC]: add stats/base/ndarray/dzscore
• [RFC]: add stats/base/ndarray/szscore
• [RFC]: add stats/base/ndarray/zscore
• [RFC]: add blas/ext/zscore