How to change a sign of elements in a matrix for each coulmn separatly ?

I want to change

v = [-2 3 0.5 4 22 15 -19 -0.01 104 78]

to

vny = [-2 -3 0.5 -4 22 -15 -19 0.01 104 -78]

thanks for tips

[Adam]

What is the logic behind which columns you want to change? Just every other column? If there is none then obviously you will have to do it manually (or at least create a multiplier array manually).

Answer 1

[Adam]

vny = v;
vny( 2:2:end) = -vny( 2:2:end);

should work