; docformat = 'rst' ; ; NAME: ; cgLogGen ; ; PURPOSE: ; This function creates an evenly spaced vector of points in log space. ; ;******************************************************************************************; ; ; ; Copyright (c) 2012, by Fanning Software Consulting, Inc. All rights reserved. ; ; ; ; Redistribution and use in source and binary forms, with or without ; ; modification, are permitted provided that the following conditions are met: ; ; ; ; * Redistributions of source code must retain the above copyright ; ; notice, this list of conditions and the following disclaimer. ; ; * Redistributions in binary form must reproduce the above copyright ; ; notice, this list of conditions and the following disclaimer in the ; ; documentation and/or other materials provided with the distribution. ; ; * Neither the name of Fanning Software Consulting, Inc. nor the names of its ; ; contributors may be used to endorse or promote products derived from this ; ; software without specific prior written permission. ; ; ; ; THIS SOFTWARE IS PROVIDED BY FANNING SOFTWARE CONSULTING, INC. ''AS IS'' AND ANY ; ; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ; ; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT ; ; SHALL FANNING SOFTWARE CONSULTING, INC. BE LIABLE FOR ANY DIRECT, INDIRECT, ; ; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED ; ; TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; ; ; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ; ; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ; ; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS ; ; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ; ;******************************************************************************************; ; ;+ ; This function creates an evenly spaced vector of points in log space. ; ; :Categories: ; Math, Utilities ; ; :Returns: ; A vector of values, evenly spaced along a log axis. ; ; :Params: ; numpts: in, optional, type=integer, default=10 ; The number of points desired in the output vector. ; ; :Keywords: ; double: in, optional, type=boolean, default=0 ; Set this keyword to return the values as double precision values. ; Otherwise, floating point values are returned. ; finish: in, optional, type=float/double, default=100 ; The ending value of the vector. The output values are evenly spaced ; between `Start` and `Finish`. This value must be a positive number. ; start: in, optional, type=float/double, default=1 ; The starting value of the vector. The output values are evenly spaced ; between `Start` and `Finish`. This value must be a positive number. ; ; :Examples: ; To create 10 values evenly spaced between 5 and 15:: ; points = cgLogGen(10, Start=5, Finish=150) ; cgPlot, points, PSym=2, /YLog ; ; :Author: ; FANNING SOFTWARE CONSULTING:: ; David W. Fanning ; 1645 Sheely Drive ; Fort Collins, CO 80526 USA ; Phone: 970-221-0438 ; E-mail: david@idlcoyote.com ; Coyote's Guide to IDL Programming: http://www.idlcoyote.com ; ; :History: ; Change History:: ; Written, 17 January 2012. DWF. ; ; :Copyright: ; Copyright (c) 2012, Fanning Software Consulting, Inc. ;- FUNCTION cgLogGen, numpts, $ Double=double, $ Finish=finish, $ Start=start Compile_Opt idl2 ; Error handling. Return to caller. On_Error, 2 ; Check parameters. SetDefaultValue, numpts, 10 SetDefaultValue, finish, 100 SetDefaultValue, start, 1 SetDefaultValue, double, 0, /Boolean ; Make sure values are positive. IF start LE 0 THEN Message, 'The starting value for the vector must be a positive value.' IF finish LE 0 THEN Message, 'The ending value for the vector must be a positive value.' ; Compute the logarithms of the end points. s = ALog10(start) f = ALog10(finish) ; Create a vector of exponent values between these two end points. exponents = cgScaleVector(Findgen(numpts), s, f, Double=double) ; Return the actual values. RETURN, 10.^exponents END