| Re: Turning off math error checking for a code block [message #28897 is a reply to message #28896] |
Thu, 17 January 2002 09:26   |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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Kenneth Bowman wrote:
>
> I have an array x that is likely to have missing values in it, indicated by NaN's.
> I would like to search the array for values less than x_min. Because of the NaN's,
> WHERE generates a floating point error, e.g.,
>
> IDL> print, x
> 0.00000 NaN 2.00000 3.00000
> IDL> print, where(x lt 2.0)
> 0
> % Program caused arithmetic error: Floating illegal operand
>
> As best I understand the interaction between !EXCEPT and CHECK_MATH,
> in order to suppress this error message, while still checking errors elsewhere
> in the code, I must do the following:
>
> error = CHECK_MATH(/PRINT) ;If any errors have occurred, print
> save_except = !EXCEPT ;Save current exception flag
> !EXCEPT = 0 ;Set exception flag to 0
> i = WHERE(x LT x_min, ni) ;Find all x < x_min
> error = CHECK_MATH() ;Clear accumulated error status
> !EXCEPT = save_except ;Restore exception flag
>
> Am I making this harder than it needs to be?
The FINITE function returns 1 where the argument is finite, and 0 where
the argument is infinite *or* NaN (see p. 134 of my book). Try the
following:
x_min = 2.0
index = where(finite(x) eq 1, count)
if (count gt 0) then print, where(x[index] lt x_min)
Cheers,
Liam.
Practical IDL Programming
http://www.gumley.com/
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