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*Subject*: Re: How do I prevent underflow errors?*From*: Craig Markwardt <craigmnet(at)astrog.physics.wisc.edu>*Date*: 17 Feb 1999 00:08:01 -0600*Newsgroups*: comp.lang.idl-pvwave*Organization*: U. Wisc. Madison Physics -- Compact Objects*References*: <36CA3B68.7C086E1B@earthling.net>*Reply-To*: craigmnet(at)astrog.physics.wisc.edu*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:13653

Phillip & Suzanne David <pdavid@earthling.net> writes: > > I have a large array of data that I'd like to plot with the contour routine. > However, the dynamic range of the data is very large, with values as large as > 1e36 and as small as 1e-40. I noticed that contour accepts float data, not > double data. This data is outside the range of float data, so it needs to be > scaled for the contour routine. I don't really care to differentiate the > 1e-40 from 0, but would like to be able to handle values up to the 1e36. I > was going to scale the data by the largest value (i.e., > PlotData=Float(Data/Max(Abs(Data)))). This puts the data in the range of -1.0 > to 1.0. This should be fine for Contour, but I get an underflow error when > converting from double data to float data. I understand that the data will > come out with a 0 instead of 1e-76, and don't really care. How do I get IDL > to ignore the underflow and just convert the value? > > Phillip > Greetings, Try the following with check_math(), which is documented in IDL. dummy = check_math(1, 1) .... commands with math errors are placed here ... dummy = check_math(0, 0) Most of your messages will go away (except for maybe the last one). Craig -- -------------------------------------------------------------------------- Craig B. Markwardt, Ph.D. EMAIL: craigmnet@astrog.physics.wisc.edu Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response --------------------------------------------------------------------------

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