Test+Problem+IDL+Analysis

=IDL Procedures for Data Analysis= Pages: Workshop, Overview, CADAC, Data Access, Work Area Setup, Path Setup, Utilities, Grid Data, SPH Data, Running, Reporting, LOG

To be able to use the IDL procedures for data analysis you need to first setup the IDL search path. Brief descriptions of procedure parameters etc may be obtained by the standard IDL self-documentation feature, **DOC_LIBRARY**. Example: code IDL> doc_library,'structurefn' code code IDL> .compile -t structurefn code or open the file in a text editor. To find the location of a **plot_power** in the file system, use code IDL> findpro,'structurefn' code
 * DOC_LIBRARY** simply lists the comment lines at the top of the procedure, between a **;+** and a **;-** line. For more details about a procedure, compile it with source listing turned on, as in

Power spectra
To compute the **power spectrum** of the 3-D array **ux**, compensated with a factor k^2.0, and fit a straight line over a given k-interval, do code IDL> power3d,ux,/aver,compensate=2.0,fit=[3,20] code To add up the contributions for all three components, do code IDL> power3d,ux,uy,uz,/aver,compensate=2.0,fit=[3,20] code

Probability Distribution Functions
To compute the PFD of density and plot it on a log log scale, do code plhist,rho,/pdf,/xlog,/ylog code To fit the central parts to a parabola, thus determining the "b" in the relation math \sigma_{\rho} = b\,\, \mbox{Mach} math add a **fit** option: code IDL> plhist,rho,/pdf,/xlog,/ylog,fit=[-2,2],b=b,Mach=7             : (yet to be implemented) code assuming the rms Mach number of the snapshot (which is the same is the rms velocity) is 7. Or else, let the fit just determine the sigma: code IDL> plhist,rho,/pdf,/xlog,/ylog,fit=[-2,2],sigma=sigma            : (yet to be implemented) code To pick up the actual histogram y-values, and the x-scale, do code IDL> plhist,rho,...[as above]...,,histogram=y,scale=x code Note: The /FIT option requires a comprehensive IDL search path -- please report problems (e.g. "missing routines").

Structure functions
These may be computed as follows: code IDL> sf=structurefn(ux,uy,uz) code with the three velocity components as input arguments. For more information, including about what is returned, see code IDL> doc_library,'structurefn' code Computing the structure function starts getting //really// slow at 512^3, so there one can choose to either subsample, code IDL> sf=structurefn(ux,uy,uz),subsample=2 code or else use the g2sf.x Fortran utility.