comp.lang.idl-pvwave archive - RDF feed
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description: Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
items: cubic spline fitting
items: Re: cubic spline fitting

cubic spline fitting
type: item
description: I am trying to use the IDL routines spl_init and spl_interp to do a cubic spline fit to variables that are vectors with 45 elements. ie y is not a function of x. I am getting 2 compilation errors where it seems to be objecting to using a vector for y instead of y being a function of x. IDL> .compile -v 'C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro' % Compiled module: LOAD_MOLDATA. spl_init,(x_nH_5,y_Tb13N_5,double) ^ % Syntax error. At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 476 spl_interp,(x_nH_5,y_Tb13N_5,x2_nH_5,y2_13N_5,double) ^ % Syntax error. At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 481 % 2 Compilation error(s) in module $MAIN$. Is my diagnosis correct? Is there a way around this problem ? I would appreciate some help. Regards Ian Smith Dept of Science and Engineering Macquarie University
date: 2014-11-14T02:18:33-00:00

Re: cubic spline fitting
type: item
description: The documentation gives an example of how to call spl_init and spl_interp X = (FINDGEN(21)/20.0) * 2.0 * !PI Y = SIN(X) ; Calculate interpolating cubic spline: Y2 = SPL_INIT(X, Y) ; Define the X values P at which we desire interpolated Y values: X2= FINDGEN(11)/11.0 * !PI ; Calculate the interpolated Y values corresponding to X2[i]: result = SPL_INTERP(X, Y, Y2, X2) PRINT, result Note that (1) there is no comma prior to the parentheses (2) one must set the output equal to a variable e.g. Y = SPL_INTERP(X,Y,Y2,X2) The confusion may be due to the fact that IDL has both procedure calls and function calls, with quite different syntax. On Thursday, November 13, 2014 9:18:36 PM UTC-5, ian....@mq.edu.au wrote: > I am trying to use the IDL routines > > spl_init and spl_interp > > to do a cubic spline fit to variables that are vectors with 45 elements. > ie y is not a function of x. > > I am getting 2 compilation errors where it seems to be objecting to using a vector for y instead of y being a function of x. > > IDL> .compile -v 'C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro' > % Compiled module: LOAD_MOLDATA. > > spl_init,(x_nH_5,y_Tb13N_5,double) > ^ > % Syntax error. > At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 476 > > spl_interp,(x_nH_5,y_Tb13N_5,x2_nH_5,y2_13N_5,double) > ^ > % Syntax error. > At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 481 > % 2 Compilation error(s) in module $MAIN$. >
creator: wlandsman
date: 2014-11-14T02:50:57-00:00

Re: cubic spline fitting
type: item
description: Thank you for your help. I can report that your suggested approach works even where the Y variable in the SPL_INIT procedure is an array of discrete values and not a function of X On Friday, November 14, 2014 1:51:01 PM UTC+11, wlandsman wrote: > The documentation gives an example of how to call spl_init and spl_interp > > X = (FINDGEN(21)/20.0) * 2.0 * !PI > Y = SIN(X) > ; Calculate interpolating cubic spline: > Y2 = SPL_INIT(X, Y) > ; Define the X values P at which we desire interpolated Y values: > X2= FINDGEN(11)/11.0 * !PI > ; Calculate the interpolated Y values corresponding to X2[i]: > result = SPL_INTERP(X, Y, Y2, X2) > PRINT, result > > Note that > (1) there is no comma prior to the parentheses > (2) one must set the output equal to a variable e.g. Y = SPL_INTERP(X,Y,Y2,X2) > > The confusion may be due to the fact that IDL has both procedure calls and function calls, with quite different syntax. > > > On Thursday, November 13, 2014 9:18:36 PM UTC-5, ian....@mq.edu.au wrote: >> I am trying to use the IDL routines >> >> spl_init and spl_interp >> >> to do a cubic spline fit to variables that are vectors with 45 elements. >> ie y is not a function of x. >> >> I am getting 2 compilation errors where it seems to be objecting to using a vector for y instead of y being a function of x. >> >> IDL> .compile -v 'C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro' >> % Compiled module: LOAD_MOLDATA. >> >> spl_init,(x_nH_5,y_Tb13N_5,double) >> ^ >> % Syntax error. >> At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 476 >> >> spl_interp,(x_nH_5,y_Tb13N_5,x2_nH_5,y2_13N_5,double) >> ^ >> % Syntax error. >> At: C:\Ian_Plots\complines 27102014 FYZ Clumps SiO 2-1 and 5-4 Peak Tbs dV30.pro, Line 481 >> % 2 Compilation error(s) in module $MAIN$. >>
date: 2014-11-19T04:22:13-00:00