# How to find and replace stand alone values in a logical array

5 views (last 30 days)
Teddy Fisher on 19 Dec 2019
Commented: Teddy Fisher on 26 Feb 2020
Hello,
I have a logical aray, a 370x29 matrix. I am trying to find all 1s and 0s that are non-consecuitve and replace them with the other one, in each column. So in a series: 00000100000 I want to be able to find and replace that stand alone 1 with a 0, and in a series: 1111101111 I want to find and replace that 0 with a 1. So far, I have been able to find and replace these with this script, where a is my 370x29 matrix:
x=find(a(diff(a)==1),1,1);
y=find(a(diff(a)==-1),1,1);
a(x)=0;
a(y)=1
The only problem with this is that it also finds and replaces the first 1 in a string of 1s and the first 0 in a string of 0s.
Is there any way to find and replace these stand alone 1s and 0s?
Thanks :)

the cyclist on 19 Dec 2019
I think this does what you want:
a(strfind([1 a 1],[1 0 1])) = 1;
a(strfind([0 a 0],[0 1 0])) = 0;
##### 3 CommentsShow 1 older commentHide 1 older comment
the cyclist on 19 Dec 2019
Sorry I was not clear. My code is applied to each row. You'd need to use a loop.
I also see now that you wanted to apply to each column, not row, which makes my code slightly awkward because strfind doesn't handle column data well. However, the following should work:
% Make up an input matrix
v = [0 1 1 0 1 1 1 0 1 1 0]';
a = [v 1-v v];
for nc = 1:size(a,2)
a(strfind([1 a(:,nc)' 1],[1 0 1]),nc) = 1;
a(strfind([0 a(:,nc)' 0],[0 1 0]),nc) = 0;
end
Use your input matrix a, instead of the data I made up.
Teddy Fisher on 26 Feb 2020
Thanks! that totally works. i dont know how or why, but it does exactly what i was trying to

### Categories

Find more on Logical in Help Center and File Exchange

R2017b

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!