difference between trapz and just summing

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jenka
jenka 2013-4-16
Dear everybody, I was wondering what is the difference between the function trapz and the sum as used below. It appears to be about the same. I am just trying to find the intersection between two histograms:
h = [16, 45, 23, 1]
g = [18, 38, 27, 5]
hn = h./sum(h);
gn = g./sum(g);
intersection = trapz(min([hn;gn]);
intersection = sum(min([hn;gn]));
Which one would be favorable over the other. It appears trapz should be better approximation.

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回答（1 个）

Matt J
Matt J 2013-4-16
If the function you've sampled and are integrating is piece-wise constant, then summing its samples will be ideal. If instead, it is piece-wise linear, the trapezoidal approximation will be ideal. You have to decide which situation more accurately describes your function.

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