# Using for loop to extract data from a matrix

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Brendan Görres 2020년 10월 3일
댓글: Brendan Görres 2020년 10월 3일
I am trying to etract certain data from a matrix into a single row vector with the length of the vector depending on the number of elements in the atrix.
So for example I extracted successfully the element numbers that represents one building component with the following code:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Assign Elements to part Cavity
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
groupc=strfind(aName,'Cavity');
tf= cellfun('isempty',groupc); %tf gives 1, if cell contains []
for i=1:length(tf) %converts [] to 0
if tf(i)==1
groupc(i)={0};
end
end
groupc=cell2mat(groupc);
combic= [aElements,groupc]; %aElements is defined as a cell array containing all existing Element number of the whole building model
cavity= ones(length(aElements),1);
n=1;
for j=1:length(aElements)
if combic(j,groupc(j)==1)
cavity(n)=combic(j,1);
n=n+1;
end
end
The result "cavity" I get is attached to this question. What I want is the loop to stop, before filling out the rows with "1" and give out a vector that has the length of the number of elements that belong to one part (in this case to the part cavity). How can I do that?
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Brendan Görres 2020년 10월 3일
the problem was the preallocation. I missed that.

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### 채택된 답변

The break statement terminates the for loop:
if j > numel(cavity)
break
end

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