How do I efficiently remove unwanted data points from a complex data structure?

I have a fairly complex structure S containing data with multiple fields (more than 40). Some of the structure fields are simple vector arrays (Nx1) but many are 2D arrays (NxM). I need to filter the data based on fairly simple criteria (e.g. if S.field1 > 1 or S.field5 == 0 etc.). When I use a loop to go through all N rows of the structure it is painfully slow (N can be > 100,000). Is there a more efficient way to do this, especially for the NxM fields? Thank you in advance.

Answer 1

[Walter Roberson]

mask = S.field1 > 1;
new_S = structfun(@(F) F(mask,:), S, 'Uniform', 0);

[HRmatlab]

You are Matlab God! Thank you.