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check inside a loop?

  • To: mathgroup at
  • Subject: [mg80736] check inside a loop?
  • From: "Jeremy Price" <cfgauss at>
  • Date: Thu, 30 Aug 2007 23:41:07 -0400 (EDT)
  • Organization: University of Washington

I have a large loop that is ndsolving/nintegrating a bunch of things, and a 
lot of the results give me various errors due to the equations not being 
very nice.  I'd like to have a way to check what values of my paramaters are 
causing the errors, but I can't find a way to do that inside a loop.

For example, if I have something like,
f[x_] = 1/Sin[2 pi x]

For[ i=1, i < 1000, i++,

I'm going to get a lot of "Power::infy: Infinite expression 1/0 
encountered." errors.  I'd like to see what values of i these occur at.

I've tried something like

For[ i=1, i<1000, i++,
Check[ f[i] , i]

But this just returns "Power::infy: Infinite expression 1/0 encountered." 
errors without the i vaule, which is different than I get by evaluating 
something like
Check[ f[0],0]
Which returns:
Power::infy: Infinite expression 1/0 encountered.

Is there any way I can get it to return the index that the error occured at 
for every error that occurs inside of the loop? 

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