The highpass and lowpass functions can be used to perform one dimensional filtering. Let us consider the following snippet:
Here if x is a matrix, then the function filters each column inependently. To apply filtering across a row, we can take the transpose of the input signal, compute the filtered output and take the transpose of the output again. The following snippet demonstrates the operation.
y_tr = highpass(x',wpass)
y = y_tr';
Similarly, we can perform the operation for lowpass filters.
Hope this helps!