How to replace zeros in a matrix by the elements of an array?

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Julius
Julius 2012-6-6
Hi everybody! I have a matrix (A) that contains zeros but it may contain also ones.
R=1:8; A=[1 0 0 0;
0 0 0 0;
1 0 1 1]
How to replace all the ones by zeros and all the zeros by elements of an array (R) going column-wise so that the resulting matrix (B) would look like:
B=[0 2 5 7;
1 3 6 8;
0 4 0 0]
  2 个评论
Thomas
Thomas 2012-6-6
I think this might be homework.. can you show what you have done so far?
Julius
Julius 2012-6-6
Yes, I've done this:
D=3;
N=4;
A=zeros(D,N);
equations=sum(A(:)==0);
R=1:equations;
for j=1:N
for i=1:D
if A(i,j)==1
A(i,j)=0;
else
ID(i,j)=?????;
end
end
end
B=A
....but I don't know how to continue

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采纳的回答

Thomas
Thomas 2012-6-6
You are on the right track, though it can be done in much simpler way but since you are a beginner this will suffice..
use
Your input matrix was zeros, just add a count for R values
Editing your code:
A=[1 0 0 0;
0 0 0 0;
1 0 1 1]
D=3;
N=4;
% A=zeros(D,N);
equations=sum(A(:)==0);
R=1:equations;
count=1;
for j=1:N
for i=1:D
if A(i,j)==1
A(i,j)=0;
else
ID(i,j)=R(count);
count=count+1;
end
end
end
ID
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更多回答（1 个）

Image Analyst
Image Analyst 2012-6-6
R=1:8;
A=[1 0 0 0;
0 0 0 0;
1 0 1 1]
linearIndices = A == 0
B = A; % Make a copy.
B(A==1) = 0
B(linearIndices) = R;
This is a vectorized way of doing it rather than your for loop method.
  1 个评论
Julius
Julius 2012-6-6
I just wanted to write down that the answer for your question is: B(A==0)=R.Meanwhile, you have done it instead of me. I just tried it and it worked. It wouldn't even cross my mind to do it that way. And it seems to be a faster code than the mine one. Thank you!

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