/**
* Standardize the matrix entries by row- or column-wise z-scores (z=(x-u)/sigma)
*
* @param isByRow standardize by row if true; otherwise by column
*/
public void standardize(boolean isByRow) {
int iters = isByRow ? numRows : numColumns;
for (int iter = 0; iter < iters; iter++) {
SparseVector vec = isByRow ? row(iter) : column(iter);
if (vec.getCount() > 0) {
double[] data = vec.getData();
double mu = Stats.mean(data);
double sigma = Stats.sd(data, mu);
for (VectorEntry ve : vec) {
int idx = ve.index();
double val = ve.get();
double z = (val - mu) / sigma;
if (isByRow) this.set(iter, idx, z);
else this.set(idx, iter, z);
}
}
}
}
/** @return sum of matrix data */
public double sum() {
return Stats.sum(rowData);
}