How to count the numbers before consecutive negative values?

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Tawsif Mostafiz
Tawsif Mostafiz 2021-7-31
评论： Tawsif Mostafiz 2021-7-31
Hi, I have a code, whose output is:
c =
0.4855 -0.1902 -0.1758 0.3935 -0.1264 -0.1274 -0.0914 -0.1149 -0.0930 0.5572 0.5098 1.0000
0.9737 0.9508 0.9046 0.9083 0.8997
Now, I want to calculate the maximum number of consecutive negative numbers (in this case, it is, 5) and the number of values before it (in this case, it is 4). How do I do it?

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采纳的回答

Image Analyst
Image Analyst 2021-7-31
Try this:
mask = bwareafilt(c < 0, 1);
props = regionprops(mask, 'Area', 'PixelIdxList')
longestRun = props.Area % Will be 5
numbersBefore = props.PixelIdxList(1) - 1 % will be 4

更多回答（1 个）

Walter Roberson
Walter Roberson 2021-7-31
Ran in:
c = [
0.4855 -0.1902 -0.1758 0.3935 -0.1264 -0.1274 -0.0914 -0.1149 -0.0930 0.5572 0.5098 1.0000 ...
0.9737 0.9508 0.9046 0.9083 0.8997]
c = 1×17
0.4855 -0.1902 -0.1758 0.3935 -0.1264 -0.1274 -0.0914 -0.1149 -0.0930 0.5572 0.5098 1.0000 0.9737 0.9508 0.9046 0.9083 0.8997
mask = c < 0
mask = 1×17 logical array
0 1 1 0 1 1 1 1 1 0 0 0 0 0 0 0 0
starts = strfind([0 mask], [0 1 1])
starts = 1×2
2 5
stops = strfind([mask 0], [1 1 0]) + 1
stops = 1×2
3 9
runlengths = stops - starts + 1
runlengths = 1×2
2 5
[maxrunlength, idx] = max(runlengths)
maxrunlength = 5
idx = 2
num_items_before_run = starts(idx) - 1
num_items_before_run = 4

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