NAN and complex.h

NAN and complex.h

[TOMAZ]

Hi I made a program which basically averages data from a file. The data is
stored as complex float and I'm reading it with fread with no problem. Some
data are taged as NAN (at least ENVI, an image procesing soft read these
values as NAN). If I average the whole data adding a number with a NAN gives
me a NAN and my whole program fails.

What I did is the folowing which doesn't seems to work:

if(cabsf(zhhzhh)!= NAN)
{
    printf("%f\n", cabsf(zhhzhh));
}

For some reason the test seeams to be positive all the time, I keep printing
NAN's ("nan" actualy).

Any idea?

  Tomas

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Re: NAN and complex.h

[Glynn Clements]

TOMAZ wrote:

> Hi I made a program which basically averages data from a file. The data is
> stored as complex float and I'm reading it with fread with no problem. Some
> data are taged as NAN (at least ENVI, an image procesing soft read these
> values as NAN). If I average the whole data adding a number with a NAN gives
> me a NAN and my whole program fails.
> 
> What I did is the folowing which doesn't seems to work:
> 
> if(cabsf(zhhzhh)!= NAN)
> {
>     printf("%f\n", cabsf(zhhzhh));
> }
> 
> For some reason the test seeams to be positive all the time, I keep printing
> NAN's ("nan" actualy).
> 
> Any idea?

NaN is not equal to anything, including itself.

To test for NaN, use isnan(). If you don't have isnan() (it's C99, not
C89), test whether "x != x" (true for NaN, false for everything else).

-- 
Glynn Clements <glynn@gclements.plus.com>

Re: NAN and complex.h

[Lukasz Mielicki]

> Hi I made a program which basically averages data from a file. The data is
> stored as complex float and I'm reading it with fread with no problem. 
> Some
> data are taged as NAN (at least ENVI, an image procesing soft read these
> values as NAN). If I average the whole data adding a number with a NAN 
> gives
> me a NAN and my whole program fails.
>
> What I did is the folowing which doesn't seems to work:
>
> if(cabsf(zhhzhh)!= NAN)
> {
>    printf("%f\n", cabsf(zhhzhh));
> }
>
> For some reason the test seeams to be positive all the time, I keep 
> printing
> NAN's ("nan" actualy).
>
> Any idea?

use isnan or isfinite to check for wrong values

BX