How to make alternating signs on a matrix?

E=[1:4;6:9;11:14;16:19]

So I have this matrix, how can i make it so that the components come one with + sign and one with - sign, so alternating signs?

We just got started today with Matlab so sorry if it is a beginners question

Answer 1

[Star Strider]

Another approach:

E=[1:4;6:9;11:14;16:19];
m = (-1).^toeplitz((1:size(E,1)),(1:size(E,2)));        % Multiplier Matrix
Out = E .* m

producing:

Out =
    -1     2    -3     4
     6    -7     8    -9
   -11    12   -13    14
    16   -17    18   -19

Create ‘Out’ by multiplying them in the same line if you want. (I kept them separate for clarity.)

Answer 2

[Fangjun Jiang]

There are many ways. This is probably the easiest.

E(1:2:end) is the 1, 3, 5,... th element of the matrix

E(2:2:end) is the 2,4,6,...th element of the matrix, so

E(1:2:end)=-E(1:2:end)

or E(2:2:end)=-E(2:2:end)