delete the columns with the last two values equal to NAN

Hi all, I have a matrix

a=[1 NaN 1 1; 1 1 1 1; NaN NaN NaN 1;NaN NaN 1 NaN ]

How to do the function that deletes the columns whose last two values are NaN? So the a matrix here is expected to be

b=[1 1;  1 1; NaN 1; 1 NaN ]

after the first and second column are deleted from the matrix.

a =
     1   NaN     1     1
     1     1     1     1
   NaN   NaN   NaN     1
   NaN   NaN     1   NaN
b =
     1     1
     1     1
   NaN     1
     1   NaN

Thank you very much.

Answer 1

[Renato Agurto]

This should do it:

 b = a(:, ~isnan(a(end-1,:)) | ~isnan(a(end,:)));

[Guillaume]

Alternatively,

b = a(:, ~all(isnan(a(end-1:end, :))));