# How to count the numbers before consecutive negative values?

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Tawsif Mostafiz on 31 Jul 2021
Commented: Tawsif Mostafiz on 31 Jul 2021
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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Tawsif Mostafiz on 31 Jul 2021
Thanks!

Image Analyst on 31 Jul 2021
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

### More Answers (1)

Walter Roberson on 31 Jul 2021
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

R2021a

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