MATLAB: How to extract indices with a condition

boolconditionindicesvector

For example I have Y = X(X==42), but I need the indices also!

To find the index where X is equal to 42, type

 idx=find(X==42)
 Y=X(idx)

function idx = maxidx(x)
  [~, idx] = max(x);
function idx = minidx(x)
  [~, idx] = min(x);

Together with

 accumarray(OrbNO,elev,[],@(x) maxidx(x)-minidx(x), 0);

Yes.

Xeq1 = numel(index);

This is how I would do it.