'How to find NaN in an array and stop once found?

Say, I want a routine to stop once a not-a-number is found in an array. How can I do this?

if (array(i) .eq. NA) ... seems not work.

The array is an array of floating point numbers:

REAL :: array(35)

arraysfortran


Solution 1:[1]

If you are really looking for NaNs and you have an up to date compiler then the ieee_is_nan() function should do the trick. I think you'll need to use ieee_arithmetic or one of the other intrinsic IEEE modules.

If your compiler is not so new, it may have the commonly-implemented but non-standard isnan() function.

Solution 2:[2]

You question is not very well constrained. Is array an array of strings? e.g.

character(len=20) :: array(40)

If this is the case, you should be able to just do:

do i=1,40
   if(array(i).eq."NA")then
       exit
   else
       !do something else
   endif
enddo

If this is an array of floating point numbers (and NA is defined to be some floating point constant), you might want to be careful as floating-point operations are rarely exact and rounding error can cause a calculation that would mathematically be equivalent to actually evaluate to different values. In other words, the solution to this problem really depends on how NA and array are declared...

Sources

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Source: Stack Overflow

Solution Source
Solution 1 High Performance Mark
Solution 2 mgilson

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