How to calculate the number of consecutive negative values in an array before a positive appears?

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Tawsif Mostafiz
Tawsif Mostafiz 2021-7-29
评论： Image Analyst 2021-7-30
I am writing a code, where the output is as follows:
c =
-0.4607 -0.4659 -0.5165 -0.5168 -0.5164 -0.4626 -0.4668 -0.3730 -0.3426 0.3224
0.3251 0.3270 0.3281 0.3400 -0.1816 -0.1830 -0.1851 1
I want to calculate the number of negative values before a positive value appeares for each cases. How do I do that?

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Image Analyst
Image Analyst 2021-7-29
Here's another way:
c =[-0.4607 -0.4659 -0.5165 -0.5168 -0.5164 -0.4626 -0.4668 -0.3730 -0.3426 0.3224 ...
0.3251 0.3270 0.3281 0.3400 -0.1816 -0.1830 -0.1851 1]
props = regionprops(c<0, 'Area'); % Measure lengths of all runs of negative values.
results = [props.Area] % [9, 3] % Turn from structure into a vector.
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Tawsif Mostafiz
Tawsif Mostafiz 2021-7-30
Thanks everyone! I have another problem. Suppose the output is like this:
results =
1 14 3 14
Now suppose I want to find the count of numbers (both positive and negative) before the maximum count of negative numbers appears. As the maximum 14 comes twice and I need the first instance, I am calculcating the maximum by this:
maximum=max(results);
location=find(results==maximum,1);
Now, how do I calculate, how many numbers appear before it?
Image Analyst
Image Analyst 2021-7-30
That number is simply the location minus 1. So it finds 14 at location 2 for the max, and there is one number, 1, before that location.

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Adam Danz
Adam Danz 2021-7-29
Ran in:
c = [-0.4607 -0.4659 -0.5165 -0.5168 -0.5164 -0.4626 -0.4668 -0.3730 -0.3426 0.3224 ,...
0.3251 0.3270 0.3281 0.3400 -0.1816 -0.1830 -0.1851 1];
A = c(:)<0;
B = diff(find([0,A(:).',0]==0))-1;
B(B==0) = []
B = 1×2
9 3

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