change only those zeros to NaN if all in row are 0

I have

 a =

     1     2     3
     0     0     0
     2     1     0
     4     5     0
     0     0     0
     2     0     1

I need

 b =

     1     2     3
   NaN   NaN   NaN
     2     1     0
     4     5     0
   NaN   NaN   NaN
     2     0     1

i.e. only if all elements in row are 0 replace with NaN

Answer 1

[Thomas]

 a(any(a,2)==0,:)=NaN;
 b=a

[Image Analyst]

Or reverse that, if a is not supposed to change:

b=a

b(any(b, 2) == 0, :) = NaN

[per isakson]

Shouldn't that be *all*:

b( all(b, 2) == 0, :) = NaN

[Image Analyst]

It works because any() looks for non-zeros, so it's only zero if there are no non-zeros, in other words, if they are all zeros. Perhaps my answer (not my comment above) might be more intuitive though - it used all().

Answer 2

[Image Analyst]

% Make a copy so we don't change a.
b=a
% Find out which rows are all zeros.
nonZeroRows = all(b == 0, 2)
% Assign all columns of the all-zero rows to nans.
b(nonZeroRows, :) = NaN