See
doc isfinite % instead
or ~isnan()
You've written an expression for an individual element of dmii unless sac and/or xal are vectors (I'm guessing not?).
To get the row of an array, use
idx=~any(isnan(dmii),2); % column vector for no NaNs in row
res=dmii(idx,:); % select those rows.
You can, if don't need the locations for other purposes wrap the reference directly and eliminate the temporary--
res=dmii(~any(isnan(dmii),2);
