Assignment statement very time consuming

I ran the profiler on a time consuming function that I have and found that the most time consuming line of code is:

avgVal(:, :, k) = mean(val);

I preallocate the avgVal and val is an array of numbers. I'm wondering is there something I'm doing that is inefficient? The only reason I could think of is that the first and second dimensions of avgVal are large so this statement is requiring a lot of entries to be filled in.

Is there anything that I may be overlooking?

Edit:

The size of avgVal is 4000-by-100-by-6 and the size of val is 36-by-1.

[James Tursa]

We need to see the surrounding code and the actual sizes involved.

[Bryan Ehlers]

I have added the sizes

Answer 1

[Walter Roberson]

Are you sure that you want to set an entire 4000 x 100 slice of avgVal to be the same scalar? With val being 36 by 1, mean() of it would be a scalar.

If you are doing all 6 slices, it would possibly be faster to record the 6 means as a 1 x 1 x 6 vector, and then repmat() it to the 4000 x 100 x 6 size.