In general it would help if you would show the error. In this case you are doing two things wrong:
First your convolution needs to be divided by three (or the length of the moving average)
c = conv(a(:,2),mask,'valid')/3
c =
5
8
11
14
Second, notice the size of c
. You cannot just fit c
into a
. The typical way of getting a moving average would be to use same
:
a(:,4) = conv(a(:,2),mask,'same')/3
a =
1.0000 2.0000 3.0000 2.3333
4.0000 5.0000 6.0000 5.0000
7.0000 8.0000 9.0000 8.0000
10.0000 11.0000 12.0000 11.0000
13.0000 14.0000 15.0000 14.0000
16.0000 17.0000 18.0000 10.3333
but that doesn't look like what you want.
Instead you are forced to use a couple of lines:
c = conv(a(:,2),mask,'valid')/3;
a(1:length(c),4) = c
a =
1 2 3 5
4 5 6 8
7 8 9 11
10 11 12 14
13 14 15 0
16 17 18 0