Re: summation problem

[Jaco van Gorkom <j.c.van.gorkom(at)fz-juelich.de>]

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?

Yes, there is a way:
IDL> test = [0,-1,3,4,!values.f_nan]
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:
IDL> print, test>0
      0.00000      0.00000      3.00000      4.00000          NaN
% Program caused arithmetic error: Floating illegal operand

> I guess this is a simple problem, but would appreciate any help
It is simple enough, but only once you know the solution.

cheers,
  Jaco