count number of indices

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gummiyummi
gummiyummi 2020-8-6
编辑： Matt J 2020-8-8
I have an array with 7 columns filled with data. Column 2 has 0s then a 1 then 0s and then a -1 in repeating order. The number of 0s between a 1 and a -1 varies.
In column 2 I want to count for each cell which has the value 1, the number of cells there are until the next cell with value -1. If the count is bigger than 100, I want to add the index of the cell with value 1, to the first available cell in column 8.
I have come furthest with the following code:
n=1;
for i = 1:length(arrayA)
if arrayA(i,2) == 1
if abs(find(arrayA(i,2)==1) - find(arrayA(:,2)==-1)) > 200
arrayA(n,8)=i;
n=n+1;
end
end
end
yet column 8 still doesn't have any values when I run the whole thing.
Pretty sure the problem is line 3 but have no more ideas left on how I could make it work...
  2 个评论
Rik
Rik 2020-8-6
Where do you define n? Also, find might return multiple values, in which case you have a logical array for you if statement, which I always have to look up what it does. Are you sure you implemented that line correctly?
gummiyummi
gummiyummi 2020-8-7
I defined n before the for loop as follows
n = 1;
sorry forgot to include that

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采纳的回答

gummiyummi
gummiyummi 2020-8-7
n=1;
I=find(arrayA(:,2)==1);
J=find(arrayA(:,2)==-1);
for k=1:length(I)
if J(k)-I(k)>100
arrayA(n,8)=pos_one(k);
arrayA(n,9)=neg_one(k);
n=n+1;
end
end
  2 个评论
Rik
Rik 2020-8-7
If the number of elements in I and J are equal, you can use find to remove the loop.

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更多回答（1 个）

Matt J
Matt J 2020-8-6
编辑：Matt J 2020-8-6
Using group1s from the File Exchange
https://www.mathworks.com/matlabcentral/fileexchange/78008-group1s
col2=arrayA(:,2);
I=find(col2==1);
H=histcounts(nonzeros(group1s(~abs(col2))));
loc=I(H(2:2:end)>100);
arrayA(loc,8)=loc;
  3 个评论
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gummiyummi
gummiyummi 2020-8-7
group1s doesn't work since my array never has consecutive 1s
Matt J
Matt J 2020-8-8
编辑：Matt J 2020-8-8
It worked fine for me:
col2=[0,1,0,-1,0,1,0,-1,0,1,zeros(1,101),-1].';
I=find(col2==1);
H=histcounts(nonzeros(group1s(~abs(col2))));
loc=I(H(2:2:end)>100)
Notice that only the 1 at position loc=10 is picked out:
loc =
10

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