Re: [netcdfgroup] how to change a missing value

• To: Chris Barker <chris.barker@xxxxxxxx>
• Subject: Re: [netcdfgroup] how to change a missing value
• From: Ryo Furue <ryofurue@xxxxxxxxx>
• Date: Tue, 22 Apr 2025 12:15:09 +0900

Chris,


Having said that, NaN is usually "safer" in that its use causes error,
>> making your bugs easier to spot.
>>
>
> agreed, I like NaN as a fill value, but there's a downside -- NaN dpes not
> equal NaN, so code that does:
>
> if something == fill_value:
>
> Will not work. It can be tricky.
>


That's exactly the reason for the "isnan()" function:

if (isnan(fill_value)) . . .


The Fortran language also includes such a function as part of its language
standard:

use:: ieee_arithmetic

if (ieee_is_nan(fill_value)) then
. . .


In addition, Fortran compilers tend to include a compile option to enable
"floating-point exception traps". If you enable the "invalid value" trap at
the compile time, at the runtime, the program stops with an error message
as soon as a NaN is generated or operated upon. This sometimes helps debug
your code.

Ryo

• Follow-Ups:
  • Re: [netcdfgroup] how to change a missing value
    • From: Nick Humphries

• References:
  • [netcdfgroup] how to change a missing value
    • From: Cathy Smith
  • Re: [netcdfgroup] how to change a missing value
    • From: Ryo Furue
  • Re: [netcdfgroup] how to change a missing value
    • From: Chris Barker