find nan and eliminate it in matrix

hi!

i wann explain may problem with an example:

    % A=[1 2 3;5 4 6;nan nan nan]
to eleminate nan: A=(A(~isnan(A)));
i get this array:A=[1 2 3 5 4  6];

why not A=[1 2 3; 5 4 6]?

i know we could use reshape. is there any other method?

thanx

Answer 1

[the cyclist]

The reason that a vector rather than a matrix is returned is that MATLAB doesn't know that your "mask" is going to still be rectangular. For example, if your input had been

A = [1 2; 3 NaN];

then your code wouldn't be able to return a matrix.

As Walter's question suggests, you'll need to decide what to do about partial-NaN rows. Probably one of the following is what you want:

% Remove rows with all NaN:
A(all(isnan(A),2),:) = []

% Remove row with any NaN:
A(any(isnan(A),2),:) = []

You could do the analogous operations on columns by changing the 2's to 1's (and using the semicolon in the first index instead of the second).

Answer 2

[Walter Roberson]

What do you want to have happen if the rows contain unequal number of nans? Do you want to delete the entire row if any member of the row contains a nan? Or only delete the row if it is all nan?