How to use ISNAN function?

How to write:

if A(i+2,11) == NaN  % Originally posted as: if (i+2,11) == NaN

using ISNAN function?

Answer 1

[Matt Fig]

A = [3 nan 4];
isnan(A)

Are you wanting to check whether i+2 or 11 is a nan? Well we know that 11 is not a nan, so let's leave that out. If 'i' is not a nan then i+2 is not a nan. Thus we only have to check on 'i'. Now is 'i' the imaginary unit or are you masking this important MATLAB function by using 'i' as a loop index or other variable? If the latter, then

if isnan(i),disp('i is a nan'),end

By the way, IF statements in MATLAB pass the conditional if ALL of the elements evaluate to true. As you have it, that IF statement would never pass, no matter what 'i' is, because 11 is never a nan. I assume you meant something like:

if [i+2,11] == NaN,disp('In if'),end

[Shashank]

Sorry for not being precise but here A is a matrix with A(i+2,11) denoting the value at (i+2)th row and 11th column. I want to change that value from a "NaN" to any other real number. MATLAB doesn't allow the use of if and else loops when comparing NaNs.

[Matt Fig]

I see, you left out the A in your code (you posted (i+2,11) and not A(i+2,11))!! You said "any real number" so I use 0:

if isnan(A(i+2,11))
   A(i+2,11) = 0
end

Is it only this particular element you want to deal with, or all nans in the array A?

[Shashank]

Thanks a ton! I think I was making a mistake writing isnan inside the matrix.