Logical Indexing

Instead of a loop, you can pull out exactly the elements of a vector that satisfy a condition, directly.

v = [3, -1, 4, -1, 5, -9, 2];
positives = v(v > 0);
disp(positives)

v > 0 produces a vector of 1s and 0s (true/false) the same size as v; indexing v with that keeps only the entries where it was true.

Replacing values that match a condition

v(v < 0) = 0;
disp(v)

Why This Matters for Your Exams

This is the single biggest "write it the MATLAB way, not the C way" habit -- the loop version works, but logical indexing is shorter, faster, and what an exam model-answer will almost always use.

Try it yourself