MATLAB: Creating loop for subtracting values from matrix which size is variable.

matrix subtracting

for example

a=[y1,x1,y2,x2,….yn+1,xn+1]

I wanna subtract all y values as y_column=[y1;y2;y3;y4;…..;yn+1] and

I wanna subtract all x values as x_column=[x1;x2;x3;x4;……;xn+1]

what kind of loop I have to write for these subtracting?

out1=a(1:2:end)
out2=a(2:2:end)

Frame      = [0:size(crgb,2)-1; double(crgb)];

a=1:10
y=a(1:2:end)'
x=a(2:2:end)'