Transcript Training SIMG 211

Basic IDL Commands
SIMG 726
Rolando V. Raqueño
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Monday, July 20, 2015
Objective
• Quick Tour of IDL
• Writing IDL Programs
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Monday, July 20, 2015
Before we start
% source ~rvrpci/.simg726.rc
% typescript
% set history=100
AT THE END OF THE UNIX SESSION,
DON’T FORGET TO TYPE
% ^D
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Monday, July 20, 2015
Before we END
AT THE END OF THE UNIX SESSION,
DON’T FORGET TO TYPE
% ^D
You now have file called typescript
which contains a log of your UNIX
session
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Monday, July 20, 2015
Starting IDL in UNIX
• To start command line interface IDL
environment
% idl
• To start graphical interface IDL
environment
% idlde
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Monday, July 20, 2015
IDL Help
• MOST IMPORTANT IDL COMMAND
OF ALL
IDL> ?
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Monday, July 20, 2015
IDL Help Window
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Monday, July 20, 2015
Other IDL Help Facilities
IDL> doc_library,’moment’
• Allows specially formatted code
comments to be viewed without having
to view the source code
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Monday, July 20, 2015
General IDL Information
• N.B. Platform specific limitation
– UNIX
• File name conflict between lower and upper
case characters
– e.g.
addnum.pro
vs. AddNum.pro
• Recommend use of strictly lowercase file
names
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Monday, July 20, 2015
IDL Character Set
• IDL is not case sensitive
• Commands and arguments are delimited by
comas.
– e.g. IDL> print, a
• Comments are started by a semicolon (;)
– e.g. IDL> ; This is a comment
• Command options are set using a backslash
(/)
– e.g. IDL> tv, a, /order
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Other IDL Characters
• System variables are started with an
exclamation point (!)
e.g. IDL> print, !PI
e.g. IDL> y = sin( x*!DTOR )
• Command line continuation with $
e.g. IDL> print, 180 / $
!PI
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Monday, July 20, 2015
Other IDL Characters
• Multiple IDL commands can be
separated by the & symbol
– e.g. IDL> a=0.0 & b=1.0
• UNIX Command execution
– e.g. IDL> $ls -la
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Monday, July 20, 2015
Journal Facility of IDL
• The journal command allows you to
record all IDL activity during a particular
session
IDL> journal, ‘sequence.pro’
IDL> print, 3*5
IDL> journal
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Monday, July 20, 2015
sequence.pro
; IDL Version 3.6.1a (MacOS Macintosh)
; Journal File for Rolando Raqueño@green
; Working directory: Raqueño's Hard
Drive:Applications:ENVI:
; Date: Tue Sep 17 00:56:18 1996
print,3*5
;
15
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Sample Commands
• Some sample command
IDL>
IDL>
IDL>
IDL>
print,3*5
print,SysTime()
num = 5*12
help,num
NUM
INT
=
IDL> print,num
60
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Creating an Array
• Some sample command
IDL> num = fltarr(40)
IDL> help,num
NUM
FLOAT
= Array(40)
IDL> print,num
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
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0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
16
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
0.00000
Monday, July 20, 2015
Creating an “Indexed Array”
• Some sample command
IDL> for i=0,39 do num(i)=i
IDL> help,num
NUM
FLOAT
= Array(40)
IDL> print,num
0.00000
7.00000
14.0000
21.0000
28.0000
35.0000
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1.00000
8.00000
15.0000
22.0000
29.0000
36.0000
2.00000
9.00000
16.0000
23.0000
30.0000
37.0000
3.00000
10.0000
17.0000
24.0000
31.0000
38.0000
17
4.00000
11.0000
18.0000
25.0000
32.0000
39.0000
5.00000
12.0000
19.0000
26.0000
33.0000
6.00000
13.0000
20.0000
27.0000
34.0000
Monday, July 20, 2015
Shortcut Creating Indexed
Array
• Some sample command
IDL> num = findgen(40)
IDL> help,num
NUM
FLOAT
= Array(40)
IDL> print,num
0.00000
7.00000
14.0000
21.0000
28.0000
35.0000
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1.00000
8.00000
15.0000
22.0000
29.0000
36.0000
2.00000
9.00000
16.0000
23.0000
30.0000
37.0000
3.00000
10.0000
17.0000
24.0000
31.0000
38.0000
18
4.00000
11.0000
18.0000
25.0000
32.0000
39.0000
5.00000
12.0000
19.0000
26.0000
33.0000
6.00000
13.0000
20.0000
27.0000
34.0000
Monday, July 20, 2015
Indexed Array Example
• Some sample command
IDL> num = findgen(40)*10
IDL> print,num
0.00000
70.0000
140.000
210.000
280.000
350.000
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10.0000
80.0000
150.000
220.000
290.000
360.000
20.0000
90.0000
160.000
230.000
300.000
370.000
30.0000
100.000
170.000
240.000
310.000
380.000
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40.0000
110.000
180.000
250.000
320.000
390.000
50.0000
120.000
190.000
260.000
330.000
60.0000
130.000
200.000
270.000
340.000
Monday, July 20, 2015
Indexed Array Example
• Some sample command
IDL> num = findgen(40)*10-195
IDL> print,num
-195.000
-125.000
-55.0000
15.0000
85.0000
155.000
-185.000 -175.000 -165.000 -155.000 -145.000 -135.000
-115.000 -105.000 -95.0000 -85.0000 -75.0000 -65.0000
-45.0000 -35.0000 -25.0000 -15.0000 -5.00000
5.00000
25.0000
35.0000
45.0000
55.0000
65.0000
75.0000
95.0000
105.000
115.000
125.000
135.000
145.000
165.000
175.000
185.000
195.000
• In general you will be using a linear form
y=m*x+b
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Monday, July 20, 2015
Extracting Array Subset
• Some sample command
IDL> num1 = num(0:36)
IDL> print,num1
-195.000 -185.000 -175.000 -165.000 -155.000 -145.000 -135.000
-125.000 -115.000 -105.000 -95.0000 -85.0000 -75.0000 -65.0000
-55.0000 -45.0000 -35.0000 -25.0000 -15.0000 -5.00000
5.00000
15.0000
25.0000
35.0000
45.0000
55.0000
65.0000
75.0000
85.0000
95.0000
105.000
115.000
125.000
135.000
145.000
155.000
165.000
IDL> help,num1
NUM1
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FLOAT
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= Array(37)
Monday, July 20, 2015
Scalar Operation on Arrays
• Some sample commands
IDL> num = findgen(37)*10
IDL> print,num
0.00000
70.0000
140.000
210.000
280.000
350.000
10.0000
80.0000
150.000
220.000
290.000
360.000
20.0000
90.0000
160.000
230.000
300.000
30.0000
100.000
170.000
240.000
310.000
40.0000
110.000
180.000
250.000
320.000
50.0000
120.000
190.000
260.000
330.000
60.0000
130.000
200.000
270.000
340.000
IDL> help,num
NUM
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FLOAT
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= Array(37)
Monday, July 20, 2015
Two-Dimensional Plotting
• Displaying Two-Dimensional Graphics
IDL> line = Sin(num * !DtoR)
IDL> plot,line
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Monday, July 20, 2015
Two-Dimensional Plotting
• Displaying Two-Dimensional Graphics
IDL> plot,line
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IDL> plot,num,line
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Monday, July 20, 2015
Two-Dimensional
Plotting Options
IDL> plot,num,line,/Psym
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Monday, July 20, 2015
Two-Dimensional
Plotting Options
IDL> plot,num,line,Psym=1
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Other Plotting Options
IDL> plot,num,line,linestyle=1
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Monday, July 20, 2015
Labeling IDL Plots
IDL> plot,num,line,xrange=[0,360],$
ytitle='Sin(x)',Title='Sine Plot'
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Monday, July 20, 2015
Other Plot Facilities
IDL> plot,num,line,xrange=[0,360],$
ytitle='Sin(x)',Title='Sine Plot'
IDL> plots,[0,360],[0,0]
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Monday, July 20, 2015
Polygon Filling
IDL> loadct, 5
IDL> polyfill,num(0:18),line(0:18),color=120
IDL> polyfill,num(18:36),line(18:36),color=50
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Monday, July 20, 2015
Data File Inputs
• Copy the following files from
~rvrpci/pub/IDL/training
surface.dat
ctscan.dat
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Monday, July 20, 2015
Three-Dimensional Plotting
• Displaying Three-Dimensional Graphics
– To get the data into IDL, you will need to open a file and
read it into an array using the following commands (N.B.
this is specific for this particular data set)
IDL>
IDL>
IDL>
IDL>
IDL>
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file=‘surface.dat’
openr,lun,file,/get_lun
peak=fltarr(40,40)
readf,lun,peak
free_lun, lun
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Monday, July 20, 2015
Surface Plots
• Displaying Three-Dimensional Graphics
IDL> print, max(peak), min(peak)
IDL> surface,peak
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Monday, July 20, 2015
Surface Plots
IDL> x = findgen(40)*2.5 &
y=findgen(40)+50
IDL> surface,peak,x,y
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Monday, July 20, 2015
Color Look-up Tables
– The following command lets you view the
current colors loaded into the color look-up
tables
IDL> cindex
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Monday, July 20, 2015
Background/Foreground Colors
– The following surface command lets you
manipulate the background and foreground colors
IDL>surface,peak,background=200,color=45,
title='Surface Projection',charsize=2.0
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Monday, July 20, 2015
Shaded Surface Plotting
IDL> shade_surf, peak
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Monday, July 20, 2015
Draping Data Over a Surface
– We can drape a given surface over another one by the
following command (we read in the data snow the same
manner as peak)
IDL>shade_surf,peak,$
shade=snow
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Monday, July 20, 2015
Surface Plot Colored by Altitude
– We can generate a simple elevation color map.
IDL> shade_surf, peak, shade=bytscl(peak)
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Monday, July 20, 2015
Simple Contour Plots
– We can generate a simple contour map.
IDL> contour,peak
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Monday, July 20, 2015
Contour Plots Spacing
– We can generate a simple contour map and adjust spacing.
IDL> contour, peak, nlevels=10
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Monday, July 20, 2015
Contour Plots Labelling
– We can generate a simple contour map and label them
IDL> contour, peak, nlevels=10, /follow
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Monday, July 20, 2015
Contour Plots Spacing Adjustment
– We can generate a simple contour map and adjust spacing
along with line styles.
IDL> contour, peak, nlevels=10, c_linestyle = indgen(5)
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Monday, July 20, 2015
Colored Contour Plots
– We can generate a simple contour map and adjust spacing
along with line color.
IDL> contour, peak, nlevels=10, c_colors = indgen(5)*20+80
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Monday, July 20, 2015
Images Data
• Displaying Image Data
– You can read in image data in a manner similar to other
forms of two-dimensional data. You will need to
ascertain whether the data is an ASCII file or a binary
file
IDL>
IDL>
IDL>
IDL>
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openr, lun,’ctscan.dat’,/get_lun
scan=bytarr(256,256)
readu, lun, scan
free_lun, lun
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Monday, July 20, 2015
Image Data
• Displaying Image Data
IDL> window, /free, xsize=256, ysize=256
IDL> tvscl, scan
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Monday, July 20, 2015
Image Data
• Displaying Image Data
IDL> window, /free, xsize=256, ysize=256
IDL> tvscl, scan
IDL> tvscl,hist_equal(scan)
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Monday, July 20, 2015
Image Processing
• Displaying Image Data
IDL> window, /free, xsize=256, ysize=256
IDL> tvscl, scan
IDL> tvscl, sobel(scan)
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Monday, July 20, 2015
XLOADCT Routine
• Displaying Image Data
IDL> xloadct
IDL> tvscl, scan
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Monday, July 20, 2015
Writing IDL Programs
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Monday, July 20, 2015
General Form of an IDL Program
• Parts of an IDL program
pro program_name [, arg1, arg2, ..., argn]
IDL statement #1
IDL statement #2
.
.
.
IDL statement #n
end
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Monday, July 20, 2015
Compiling an IDL Program
• Create a program to take celsius arguments
and print out fahrenheit values
pro celsius_to_fahrenheit, celsius
print, 9/5*celsius+32
end
• To compile:
IDL> .compile celsius_to_fahrenheit.pro
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Monday, July 20, 2015
Executing an IDL Program
• To use the program in scalar mode:
IDL> c = 100.0
IDL> celsius_to_fahrenheit, c
• To use the program in array mode:
IDL> c = findgen(201)/2
IDL> celsius_to_fahrenheit, c
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Monday, July 20, 2015
General Form of an IDL Function
• Parts of an IDL function
function program_name [, arg1, arg2, ..., argn]
IDL statement #1
IDL statement #2
.
.
.
IDL statement #n
return, answer
end
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Monday, July 20, 2015
Compiling an IDL Function
• Create a function to take celsius
arguments and print out fahrenheit values
function celsius_to_fahrenheit, celsius
answer=9/5*celsius+32
return, answer
end
• To compile:
IDL> .compile celsius_to_fahrenheit.pro
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Monday, July 20, 2015
Executing an IDL Function
• To use the program:
IDL>
IDL>
IDL>
IDL>
c = findgen(201)/2
f = celsius_to_fahrenheit(c)
print, f
plot, c, f
• Equivalently:
IDL> print, celsius_to_fahrenheit(c)
IDL> plot, c, celsius_to_fahrenheit(c)
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Monday, July 20, 2015
Program Design
program file vs. function file
• Use functions in case of mathematical functions to
allow composition of functions
IDL> k=celsius_to_kelvin(fahrenheit_to_celsius(f))
• Use program file in case of process not requiring the
return of data
IDL> write_to_file,’temperature.dat’,k
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Monday, July 20, 2015
Parameter Passing in IDL
• IDL passes parameters into functions and
programs by reference
• This means parameters can be modified
through “side effect”
pro celsius_to_fahrenheit, celsius
celsius =9/5*celsius+32
end
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Monday, July 20, 2015
Problems with “Side Effect”
Parameter Passing
IDL> a=32.0
IDL> celsius_to_fahrenheit,a
% Compiled module:
CELSIUS_TO_FAHRENHEIT.
IDL> print,a
64.0000
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Monday, July 20, 2015
A Debugging Exercise
• The IDL function and program examples
celsius_to_fahrenheit all
compile, but generate incorrect answers
in some cases.
• This is left as a debugging exercise
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Monday, July 20, 2015
Hints for Statistics Problem
• Study the IDL functions
n_elements()
size()
• Try to reuse as many of the functions as
possible.
• Do not be concerned with efficiency at
this point.
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Monday, July 20, 2015