@Override
Val apply(Env env, Env.StackHelp stk, AST asts[]) {
Val v = stk.track(asts[1].exec(env));
if (v instanceof ValRow) {
ValRow vv = (ValRow) v;
return vv.slice(asts[2].columns(vv._names));
}
Frame fr = v.getFrame();
int[] cols = asts[2].columns(fr.names());
Frame fr2 = new Frame();
if (cols.length == 0) { // Empty inclusion list?
} else if (cols[0] >= 0) { // Positive (inclusion) list
if (cols[cols.length - 1] > fr.numCols())
throw new IllegalArgumentException(
"Column must be an integer from 0 to " + (fr.numCols() - 1));
for (int col : cols) fr2.add(fr.names()[col], fr.vecs()[col]);
} else { // Negative (exclusion) list
fr2 = new Frame(fr); // All of them at first
Arrays.sort(cols); // This loop depends on the values in sorted order
for (int col : cols)
if (0 <= -col - 1 && -col - 1 < fr.numCols()) fr2.remove(-col - 1); // Remove named column
}
return new ValFrame(fr2);
}
