# Using loops to populate a vector

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lauuser1 on 16 Feb 2016
Commented: Image Analyst on 16 Feb 2016
Say I have a 3x2 matrix (A) that ranges from the numbers 1 through 5. The 3 rows equals 3 different sets of numbers. I have to use a loop to populate a vector (B) that is the size 3x1 (3 for each set). This vector will populate with the first number in each set (every number in the first column).
So if the matrix A =
2 3
1 1
5 4
the vector B should be
2
1
5
How would you use the loop function to do that?

Moe_2015 on 16 Feb 2016
Edited: Moe_2015 on 16 Feb 2016
If you really need to use a for loop, this is how you could do it.
for i=1:size(A,1)
B(i,1)=A(i,1);
end
However, a more efficient way would be:
B=A(:,1)

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Image Analyst on 16 Feb 2016
Fix what? What does suppression mean to you? You mean having the value of B echo to the command window if you leave off the semicolon? If so, I'm still not sure what you want, or don't want, to see.
lauuser1 on 16 Feb 2016
What I am trying to fix is that I just want the final result of B rather than it echoing. I would like to see B in my command window as just one single fully populated 3x1 vector with no values of 0.
Image Analyst on 16 Feb 2016
Put B by itself after the loop to have it echo only the final B
for i=1:size(A,1)
B(i,1)=A(i,1); % Semicolon to suppress echo to command window.
end
% Print B to command window:
B