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*Subject*: Re: How to do polar plots with logarithmic axis in radial coordinate?*From*: Paul van Delst <pvandelst(at)ncep.noaa.gov>*Date*: Wed, 07 Feb 2001 09:21:36 -0500*Newsgroups*: comp.lang.idl-pvwave*Organization*: CIMSS @ NOAA/NCEP*References*: <3A802C71.1070002@uci.edu> <on7l33fpp7.fsf@cow.physics.wisc.edu> <3A80AEBB.8010701@uci.edu>*Xref*: news.doit.wisc.edu comp.lang.idl-pvwave:23419

Charlie Zender wrote: > > Craig Markwardt wrote: > > > Could you simply take the ALOG10() logarithm of the data before > > plotting it? Easier to re-label the axis than re-invent the world... > > > > This would cause the radial coordinate to be negative-valued which > would have unpleasant results. It's possible someone could get > this method to work but I tried without success. I did the following: IDL> r=10.0^(findgen(100)/20.0) IDL> theta=findgen(100)/5. IDL> !p.charsize=2.5 IDL> plot, alog10(r), theta, xsty=4,ysty=4,/polar IDL> axis,0,0,xax=0,xtickformat='expticks_log' % Compiled module: EXPTICKS_LOG. IDL> axis,0,0,yax=0,ytickformat='expticks_log' where the expticks_log.pro is: FUNCTION expticks_log, axis, index, value tickmark = '10!E' + $ STRTRIM(STRING(value,FORMAT='(f5.1)'),2) + $ '!N' RETURN, tickmark END The !P.CHARSIZE was just so I could see the exponents. Is this what you are looking for? Keep in mind that the format string for the expticks_log.pro won't work for exponents less than 0.0 - you'll have to get smart about checking for the range and then setting the format string based on that (rather than the f5.1 above, e.g.: CASE 1 OF ; -- Exponent is less than zero -> ; -- fractional ticklabel ( exponent LT 0 ): format = '( f' + $ STRTRIM(ABS(exponent)+2,2) + $ '.' + $ STRTRIM(ABS(exponent),2) + $ ' )' ; -- Exponent is greater than or = to zero -> ; -- whole number ticklabel ( exponent GE 0 ): format = '( i' + $ STRTRIM(ABS(exponent)+1,2) + $ ' )' ENDCASE and then use the format string in the return value, e.g. RETURN, '10!E' + STRING( value, FORMAT = format ) + '!N' or something similar depending on your tastes/needs. Hope some of this is helpful, although I have to admit, the fact that IDL doesn't have a stock polar plotting routine that produces a circular graph with the radial and concentric circle tickmark axes is a bit ridiculous. Farting about with /POLAR and AXIS and whatnot is sort of like using OG to plot, x, y - and in the end you still end up with Cartesian-like axes. Maybe there is a polar plotting routine out there in IDL software land somewhere. It is sorely needed. paulv -- Paul van Delst A little learning is a dangerous thing; CIMSS @ NOAA/NCEP Drink deep, or taste not the Pierian spring; Ph: (301)763-8000 x7274 There shallow draughts intoxicate the brain, Fax:(301)763-8545 And drinking largely sobers us again. pvandelst@ncep.noaa.gov Alexander Pope.

**Follow-Ups**:**Re: How to do polar plots with logarithmic axis in radial coordinate?***From:*Mirko Vukovic

**Re: How to do polar plots with logarithmic axis in radial coordinate?***From:*Charlie Zender

**References**:**How to do polar plots with logarithmic axis in radial coordinate?***From:*Charlie Zender

**Re: How to do polar plots with logarithmic axis in radial coordinate?***From:*Craig Markwardt

**Re: How to do polar plots with logarithmic axis in radial coordinate?***From:*Charlie Zender

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