Calculate the mean of nonzero pixels and setting a threshold

I have a 3D binary mask and a 4D array with some values. I calculate the mean of my array which corresponds to the regions of my mask.

my_mean = accumarray(double(mask(:))+1, my_array(:),[],  @nanmean, 0)

I would like to set a threshold. i.e., if the value in the array is more than 100 then ignore it from the calculation. I tried the following without success. Any help is highly appreciated.

my_mean = accumarray(double(mask(:))+1, my_array(:),[],  @nanmean, 0, my_array(:)<99)

Answer 1

[Matt J]

fun=@(z) nanmean(z(z<99));

my_mean = accumarray(double(mask(:))+1, my_array(:),[],  fun)