@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();
}
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 scale(double alpha) {
if (alpha == 0) return zero();
else if (alpha == 1) return this;
for (VectorEntry e : this) e.set(alpha * e.get());
return this;
}
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;
}
protected double norm2_robust() {
double scale = 0, ssq = 1;
for (VectorEntry e : this) {
double xval = e.get();
if (xval != 0) {
double absxi = Math.abs(xval);
if (scale < absxi) {
ssq = 1 + ssq * Math.pow(scale / absxi, 2);
scale = absxi;
} else ssq = ssq + Math.pow(absxi / scale, 2);
}
}
return scale * Math.sqrt(ssq);
}
/**
* 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);
}
}
}
}
protected double normInf() {
double max = 0;
for (VectorEntry e : this) max = Math.max(Math.abs(e.get()), max);
return max;
}
protected double norm2() {
double norm = 0;
for (VectorEntry e : this) norm += e.get() * e.get();
return Math.sqrt(norm);
}
protected double norm1() {
double sum = 0;
for (VectorEntry e : this) sum += Math.abs(e.get());
return sum;
}
