| Re: summation problem [message #24624 is a reply to message #24529] |
Thu, 05 April 2001 09:26  |
Jaco van Gorkom
Messages: 97
Registered: November 2000
|
Member |
|
|
Paul van Delst wrote:
> Jaco van Gorkom wrote:
>> Manish wrote:
>> ...
>>> I have a program which produces an array of values of sunlight flux during
>>> the day. Unfortunately, it produces crazy numbers before the sunrises and
>>> after it sets(as expected). I'm summing the values throughout the day to
>>> get a total integrated day flux, but here's the problem - is there a way of
>>> telling the TOTAL function to ignore negative numbers and NaN numbers?
>>
>> IDL> print, total(test>0,/nan)
>> 7.00000
>> % Program caused arithmetic error: Floating illegal operand
>>
>> The 'illegal operand' error appears to be harmless, caused by comparing test>0:
>
> Harmless maybe, but I for one don't like seeing illegal operand errors, let alone ignoring
> them. What if you add some code that tries to take the log of a -ve number, see the same
> error and shrug it off?
That is *exactly* what I'd do: shrug it off! The log of a -ve number gives me
-Inf as a
result, which will propagate through any calculation to be NaN, Inf, or -Inf.
Just another
missing data point.
> loc_finite = WHERE( FINITE( test ) EQ 1, count_finite )
> IF ( count_finite GT 0 ) THEN $
> sum = TOTAL( test[ loc_finite ] > 0.0 ) $
> ELSE $
> sum = !VALUES.F_NAN ; Or some other suitable flag
Of course I see your point. I would probably implement a FINITE() check if I
were writing a
full program, but the annoying special-case programming for when WHERE() returns
-1 held me
back here.
On second thought: WHERE() could only return -1 for a day without sunrise...
groetjes,
Jaco
> ...
> Oh, and make sure you set !EXCEPT = 2 in your idl setup file. That'll learn ya to remove
> errors from your code :o)
Geez! Thanks for pointing that out! This solves everything Manish: !EXCEPT = 0.
|
|
|
|
comp.lang.idl-pvwave archive
Members
Search
Help
Login
Home
