Introduction
This page is based on a CPPG Seminar given on March 7, 2000.The most effective way for you to go through these examples is by running IDL in a separate window, and trying out the commands and programs as you read. For maximum benefit, you should save copies of the programs in a personal directory, and experiment with changing them.
Getting started
You need to know about How to Setup IDL at PPPL. This will tell you on which machines IDL is running, how to set up your environment, how to set your display, and how to find documentation.
Running IDL programs can be stopped using control-C. (Hold down the control key and hit the letter c). IDL can be aborted immediately using control-\. (All variables are lost and the state of open files will be uncertain). On VMS you may have to hit control-Y if this does not work.
Basic examples at the command line interface
Try the following commands at the IDL prompt,Everything after the ";" (the IDL comment character) need not be typed.
c=mk_color(/load) ; load a structure with indices of colors a = 5 ; make a scalar print,a b = [2, 3] ; make an array print,b print,a*b ; print the product x = findgen(100) ; make an array of floating pt. indices (0, 1, 2...) print,x[30:40] ; print part of the array y=exp(x/25)*sin(x/5) ; make an interesting y array plot,x,y ; overplot another y array oplot,x,exp(-1.*x/25)*sin(x/5)*50,color=c.red yr = y + 3*randomn(seed,100) ; make a y array with random numbers added plot,x,yr,psym=4 oplot,x,y,color=c.black ; interpolate to a lower resolution x20 = interpol(x,20) y20 = interpol(yr,20) oplot,x20,y20,color=c.blue ; spline-interpolate back to original grid yfit = spline(x20,y20,x) oplot,x,yfit,color=c.red help ii=where(abs(yfit-yr) GT 5) ; find indices of points deviating from fit oplot,x(ii),yr(ii),color=c.green,psym=4 ; color outliers in green
See http://NSTX.pppl.gov/nstx/Software/IDL/idl_intro.html for more simple examples.
Examples for 2-D data
; BD class examples for contouring and surface plotting. ; can be run by typing IDL> .run ~bdavis/Clsss/contouring pro contouring PRINT, 'type ".cont" to continue, or ".so" for single steps' STOP d=dist(40) ; generate a 2-D array for illustration contour,d th_image_cont,d, /nocont ; color contours with a color bar surface,d surface,d,charsize=2 ; use keyword to increase character size surface,d, az=60 ; rotate around z axis LOADCT,3 ; load a "hot metal" color palette shade_surf,d ; shade as with a light source c=sin(d) ; make another array for shading shade_surf,d,shade=bytscl(c,top=50) show3,d ; show 3 plots on one ; for realistic data: restore,file='/u/bdavis/Class/logp.sav' ; log power of freq vs. time contour,logp surface, logp th_image_cont, logp, /nocont ; color contours with a color bar show3, logp ; the three above styles combined end
Image Processing Example Widget
IDL> restore, '/u/bdavis/Vis/imageproc.sav'
IDL> imageproc
The code for this is in /u/bdavis/Vis/imageproc.pro.
An MDS Plotter Widget
If your are running x-windows, type the following at the IDL prompt:
IDL> mdsw
Some of the above "widgets" are buttons that you click on to initiate actions (like making a plot), others are fields you can type in (like signal). This example includes pull-down menus on the menu bar. You can rescale the plot by placing the mouse pointer over the plot, holding down the middle mouse button, dragging, and releasing. The x- and y-positions of the cross-hairs are shown in the small boxes at the bottom of the plot.
To find where this source for mdsw.pro is located on your computer, type:
IDL> doc_library,'mdsw'You should probably look at mdsw_noch.pro. It is simpler and illustrates most of the important concepts.
If you want to customize your own MDSplus plotting widget, the easiest way may be to copy all the routines from /nstxusr1/util/misc/plotw on the PPPL Unix cluster, and adapt the "include" files to your purposes.
How to find out more about IDL.
See IDL On-line Help (type "?" at IDL prompt), e.g. on File Formats, Signal Processing Routines, etc. Try the Index search.
For broader-based, glitzier, demo:
IDL> demoSee, e.g.,
- Earth Science..Environmental Modeling
- Visualization..Slicer
- Data Analysis..Mathematics & Statistics
You may also want to look at the IDL supplied examples in /usr/local/rsi/idl/examples on Unix or IDL_DIR:[EXAMPLES] on VMS.
Other tutorials on IDL at PPPL are available. See IDL Introduction and Using IDL for more advanced Plotting.
You should also visit these valuable IDL sites, especially the ones that let you search for IDL routines written by others (no such search exists for fusion, or PPPL-specific software, but it should -- some locally-written routines are described at http://w3.pppl.gov/~bdavis/pppl_idl_routines.html).