Replace Nan by a number in a cell array with Matlab - matlab

Question

a = { [5 5 5 6 ] [ Nan Nan Nan Nan]; [ 7 8 8 8 ] [1 2 3 5] }
i want to replace a{1,2} by [1 1 1 1 ]
Is it possible? because I tried this function:
function k = non(a)
[l ,c ] = size(a);
for i= 1 : l
for j =1 : c
if a{i,j} == [ NaN NaN NaN NaN ]
k{i,j} = [ 1 1 1 1]
else
k{i,j} = a{i,j} ;
end
end
end
end
but it doesn't work.

Answer 1

You can define the following simple function:
function matrix = replace_nan(matrix, value)
matrix(isnan(matrix)) = value;
end
and then use cellfun to execute it over all elements of your cell array (I have generalized your problem slightly by allowing you to define value as the number to replace the NaN with, and making the elements variable length):
>> a = {[ 3 NaN] [NaN NaN NaN] [1 2 3 4 5 NaN 0 NaN]};
>> value = 1; %% the value to replace the NaN with
>> z = cellfun(#replace_nan, a, repmat( {value}, size(a,1), size(a,2)) , 'UniformOutput', 0);
>> z{1}
ans =
3 1
>> z{2}
ans =
1 1 1
>> z{3}
ans =
1 2 3 4 5 1 0 1
A few comments on the use of cellfun here: cellfun takes a function, in this case replace_nan, and a cell array, in this case a, and iterates the function call to replace_nan(). If replace_nan were a single argument function, we could say cellfun(#replace_nan, a), but the way I defined it, the function takes two arguments. The way to specify that in cellfun is to provide a second cell array with the value arguments. That is the repmat({1},size(a,1),size(a,2)) which creates a second cell array with the same dimensions as a, but filled with 1's.
EDIT: The comment discussion brings up a good point: you cannot use == to test for NaN, you must use MATLAB's isnan() function.
>> [NaN NaN] == [NaN NaN]
ans =
0 0
>> isnan( [NaN NaN] )
ans =
1 1

Answer 2

Or even shorter this way:
a(cellfun(#(cell) any(isnan(cell(:))),a))={[1 1 1 1]};