Subtraction of elements in successive rows

I have a matrix 'a'. I need an output matrix 'A' with each row equal to the difference between successive rows of the parent matrix 'a'. Is there a way to do this? I tried coding it in the following manner but keep getting an error message 'Unable to perform assignment because the left and right sides have a different number of elements.'

a=[1 2;2 4;3 6];

A=zeros(2,2);

for i=1:2

A(i)=(a(i+1,:)-a(i,:));

end

The expected result is A=[1 2; 1 2]

Answer 1

[William]

The easy way to do this is

A = diff(a);

[Stephen23]

Even better, specify the dimension:

b = diff(a,1,1)

ans = 2×2

1 2 1 2

[Shreya George]

Thanks