MATLAB: Efficiently calculating sum-thresholds across vector

for loopMATLABmoving windowsumthreshold

I have a 1xN vector of samples, for which I need to calculate the indices of when a moving sum exceeds a threshold.
One could think of the samples as current that is charging a capacitor, and once the capacitor is charged to the threshold, a pulse is fired and the capacitor is reset. I need to find the times when the pulse is fired.
I have a working loop implementation below, however, it is relatively slow and I'd like to find a more efficient method. Is there a vectorized or built-in method for finding these pulse times?
samples;
threshold = 50;
pulseIdx = zeros(size(samples));
runningSum = 0;
for i = 1:length(samples)
    runningSum = runningSum + samples(i);
    if runningSum > threshold
        pulseIdx(i) = 1;
        runningSum = runningSum - threshold; % allow spillover to next cycle
    end
end

Best Answer

You could do the following but with the caveat that it assumes samples are all positive values
runningSum = cumsum(samples);
idx = find(diff(mod(runningSum,threshold))<0)+1;
Or in the case where they are not all positive, perhaps something like the following:
idx = find(diff(mod(runningSum,50))<-0.5*threshold)+1
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