Separating Matrix Rows into two different vectors

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?

Answer 1

[Matt J]

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

[A]

Thank you for your response just wondering what is X? Where did it come from?

[Matt J]

@(X) {X} is an anonymous function. X is just a parameter of the function.

[A]

I see that makes sense,

Thank you

[Matt J]

You're welcome, but please Accept-click the answer if it resolves your question.