See https://en.wikipedia.org/wiki/Causal_filter "In signal processing, a causal filter is a linear and time-invariant causal system. The word causal indicates that the filter output depends only on past and present inputs. A filter whose output also depends on future inputs is non-causal, whereas a filter whose output depends only on future inputs is anti-causal. "
If your signal is time, with early times on the left and later times on the right, then I guess a non-causal filter would be a window that had an odd number of elements and didn't have any on the past/left side of it, like
kernel = [0,0,0,0,1,1,1,1,1] / 5;
out = imfilter(signal, 1, kernel);
or something like that.
