public double dot(Vector y) {
checkSize(y);
double ret = 0;
for (VectorEntry e : this) ret += e.get() * y.get(e.index());
return ret;
}
public Vector add(double alpha, Vector y) {
checkSize(y);
if (alpha == 0) return this;
for (VectorEntry e : y) add(e.index(), alpha * e.get());
return this;
}
public Vector set(double alpha, Vector y) {
checkSize(y);
if (alpha == 0) return zero();
zero();
for (VectorEntry e : y) set(e.index(), alpha * e.get());
return this;
}
@Override
public String toString() {
// Output into coordinate format. Indices start from 1 instead of 0
Formatter out = new Formatter();
out.format("%10d %19d\n", size, Matrices.cardinality(this));
for (VectorEntry e : this)
if (e.get() != 0) out.format("%10d % .12e\n", e.index() + 1, e.get());
return out.toString();
}
/**
* 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);
}
}
}
}
