# Separating Matrix Rows into two different vectors

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A on 23 Jan 2021
Commented: Matt J on 29 Jan 2021
I have a matrix
A=[1 3 5;1 5 6;3 9 10;3 5 6;1 4 5;3 5 6; 9 6 7; 1 5 8; 3 6 0];
and i would like to seperate in in terms of the 1st element
for example
if A(1,i)==1 then it would a adn if A(1,i)== 3 then it would go into b and i would like A to reduce in size as it goes to one matrix or another.
So when I have the first row after it gets assigned into a vector i want it to be deleted and goes to the next one
so i want my final results to look like
A=[9 6 7]
a=[1 3 5;1 5 6;1 4 5;1 5 8]
b=[3 9 10;3 5 6;3 5 6; 3 6 0]
How would that be done?
And, if I had this condition
A(1)<2 put in a matrix if greater than >2 put in b matrix. and the format would look like this:
A=[9 6 7]
a=[1 3 5;1 5 6;1 4 5;1 5 8]
b=[3 9 10;3 5 6;3 5 6; 3 6 0]
How would it be done?

Matt J on 23 Jan 2021
Edited: Matt J on 23 Jan 2021
A=[1 3 5;1 5 6;3 9 10;3 5 6;1 4 5;3 5 6; 9 6 7; 1 5 8; 3 6 0];
groups=splitapply( @(X) {X} , A , findgroups(A(:,1)) );
[a,b,A]=deal(groups{:})
a = 4×3
1 3 5 1 5 6 1 4 5 1 5 8
b = 4×3
3 9 10 3 5 6 3 5 6 3 6 0
A = 1×3
9 6 7
Matt J on 29 Jan 2021