# I have a matrix and I am actually interested in obtaining a vector that will consist of the first column in each row that has values lower certain value.

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Saint on 26 May 2017
Edited: Stephen Cobeldick on 29 May 2017
I have a matrix and I am actually interested in obtaining a vector that will consist of the first column in each row that has values lower 3. e.g if I have A=[ 5 7 8 3 2 ;6 2 1 4 4;1 2 3 4 5; 4 5 2 1 3]. I expect an Ans: [5;2;1;4]

Saint on 29 May 2017
Edited: Saint on 29 May 2017
Thanks Star Strider and MathsReallyWork. I kind of figure it out.Ans: [5;2;1;3]
dmax=3
Nrows=4
A=[5 7 8 3 2 ;6 2 1 4 4;1 2 3 4 5; 4 5 2 1 3]
for i=1:Nrows
B=A(i,:)';
a(i)=find(B<dmax,1,'first') ;
end
b=a'

#### 1 Comment

Stephen Cobeldick on 29 May 2017
It is simpler and more efficient to process the whole array at once, rather than using a loop:
>> C = A.';
>> idx = C<dmax;
>> [col,row] = find(idx & cumsum(idx,1)==1)
col =
5
2
1
3
row =
1
2
3
4

MathReallyWorks on 27 May 2017
Hello saint,