I want to smooth an image using an isotropic Gaussian filter with
standard deviation of =F3x, =F3y =3D 3.

To achieve this, can I use the fspecial function to create the
smoothing filter as follows:

gauss_filter =3D fspecial('gaussian', [x y], 3);

With [x y] being the size of the filter to apply to the image. If not,
what should I be using instead?

Also, what is the relationship between the number of filter samples
required and the standard deviation used?

Thanks.