I have a dummy vector with 5000 rows and 1 column . I have some single 1 in this vector. No I want to change all 0 before the 1 to 1 and also change the 3 following 0 after the 1 to 1. But I don't know how. Could someone help me?Thank you a lot.

In gener i would like to change

0 0 1 0 0 0 0

to

0 1 1 1 1 1 0

Answer 1

[Guillaume]

One possibility, assuming you're using R2016b:

v = [0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0];  %for example
startseq = strfind(v, [0 1 0 0 0]);  %strfind also work for finding sequences of numbers
v(startseq + (0:4)') = repmat([1 1 1 1 1], 1, numel(startseq));

If prior to R2016b, replace startseq + (0:4)' in the last line by:

bsxfun(@plus, startseq, (0:4)')

[FC93]

Thank you for your answer. Now I get an error:

Error using + Matrix dimensions must agree.

What could be wrong?

[Guillaume]

What is wrong is that you're using a version before R2016b.

As I wrote in my answer, If prior to R2016b, replace .... Follow the instructions!

[FC93]

Now I got what I wanted. Thank you very much fo your help. I just replaced startseq + (0:4)' with bsxfun(@plus, startseq, (0:4)'), but I am using MATLAB R2016a, so maybe thats why.

Have a nice day.

Answer 2

[KSSV]

A = [0 0 1 0 0 0 0] ;
B = A ;
B(A==1) = 0 ; % replace 1 with 0 
B(A==0) = 1 ; % replace 0 with 1

[Guillaume]

I don't think that's what is being asked. And more importantly, the above is just:

B = double(~A)

[KSSV]

Yes ..you are right...Guillaume

[FC93]

thank you for your answer but I have a vector with the dimensions 5000x1 and approximately 170 ones. I just need to change the 0 before the 1 to 1 and the following three 0 after the 1 to 1. Do you know how I could do it?

An example [0;0;0;0;0;0;0; 1;0;0;0;0;0;0;0;0;] to [0;0;0;0;0;0; 1; 1; 1; 1; 1;0;0;0;0;0;]

The problem is that I need a function because I have over 5000 values. Thank you

Answer 3

[Jos (10584)]

You can convolve your vector with a series of ones using filter, which will add a specific number of ones after each array

a = [0 0 1 0 0 0 0 0]
filter(ones(1,4),1,a) % add 3 ones
%   [0 0 1 1 1 1 0 0]

Using something similar on the reversed array will give you what you want.

FUN = @(V,AddN) filter(ones(1,AddN+1),1,V) % a function for convenience
V = [0 0 1 0 0 0 0 0 0 1 1 0 0]
FUN(V,3) | fliplr(FUN(fliplr(V),1)) % add 3 ones after and 1 one before each 1 in V