I have a large $100 \times 4000$ element matrix composed of integer elements,
testMatrix, and I was to use
Position to find the indices of integers larger than some threshold value
thresholdValue. The following works:
Position[testMatrix, x_ /; x >= thresholdValue, 2]
However it takes over $\approx 150$ milliseconds to execute.
Given that the number of positions is typically around $10^3$, is there a way to achieve a significant speedup for this procedure?