| Re: How does IDL calculate the graph axis values? [message #18702] |
Wed, 02 February 2000 00:00 |
mallors
Messages: 76
Registered: November 1997
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Member |
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In article <38986E90.5B2D58C8@ssec.wisc.edu>,
"Liam E. Gumley" <Liam.Gumley@ssec.wisc.edu> writes:
> Declan Vogt wrote:
>
>> I'd like to find out what IDL will use as the max and min values for a
>> graph axis before it actually plots the axis. I've been doing this by
>> creating a window, drawing the axis, and reading !x.crange, then erasing
>> the window, but it's not very elegant, and it doesn't work for
>> postscript.
>>
>> Does anyone know if there is an IDL routine I can call?
>
> I don't think there's a built-in routine for this purpose. However you can
> always use the Z buffer as a temporary graphics device:
>
> Say your data is defined as follows:
>
> x = findgen(200) * 0.1
> y = sin(x)
>
> First you save the current graphics setup:
>
> entry_device = !d.name
> entry_window = !d.window
> entry_config = {x:!x, y:!y, z:!z, map:!map}
>
> Then you create a temporary plot in the Z buffer:
>
> set_plot, 'Z'
> device, z_buffer=0
> plot, x, y, /nodata, xstyle=4, ystyle=4, /noerase, /ynozero
> xrange = !x.crange
> yrange = !y.crange
There is also the 'NULL' device to suppress
graphics output entirely:
dSave = !D.NAME
SET_PLOT, 'NULL'
.
.
.
SET_PLOT, dSave
Regards,
-bob mallozzi
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~
Robert S. Mallozzi 256-544-0887
Mail Code SD 50
http://gammaray.msfc.nasa.gov/ Marshall Space Flight Center
http://cspar.uah.edu/~mallozzir/ Huntsville, AL 35812
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~
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| Re: How does IDL calculate the graph axis values? [message #18708 is a reply to message #18702] |
Wed, 02 February 2000 00:00  |
Ben Tupper
Messages: 186
Registered: August 1999
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Senior Member |
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
"Liam E. Gumley" wrote:
<blockquote TYPE=CITE>
<br>This method does not require a graphics window to be open, does not
care
<br>what graphics device is active, does not disturb the contents of the
Z
<br>buffer, and does not disturb the current plot settings.
<br>
<br><a href="http://cimss.ssec.wisc.edu/~gumley"></a> </blockquote>
Hello,
<p>I wonder if the IDLgrAxis object might be handy here. I
haven't thought about it before, but I would guess that
<br>the axis range in Direct and Object graphics are determined in the
same way by IDL (or at least the results will be similar.)
<br>Assuming that your want to use direct graphics, you could temporarily
create an axis specifying your data range. Then use the GetProperty
method to retrieve
<br>CRange. Finally, destroy the object.
<p>Direction = 0 ; or 1 for the yaxis
<br>oAxis = Obj_New('IDLgrAxis', Direction, Range = [YourDataMin,YourDataMax])
<br>oAxis -> GetProperty, CRange = CRange
<br>Obj_Destroy, oAxis
<p>Here's what the help file on CRange states:
<p>CRANGE
<br>Set this keyword to a named variable that will contain the actual full
range of the axis as a vector of the form [minval, maxval]. This range
may not exactly match the requested range provided via the RANGE keyword
in the Init and SetProperty methods. Adjustments may have been made to
round to the nearest even tick interval or to accommodate the EXTEND keyword.
<p>Ben
<pre>--
Ben Tupper
Bigelow Laboratory for Ocean Science
tupper@seadas.bigelow.org
pemaquidriver@tidewater.net</pre>
</html>
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| Re: How does IDL calculate the graph axis values? [message #18709 is a reply to message #18702] |
Wed, 02 February 2000 00:00 |
Liam E. Gumley
Messages: 378
Registered: January 2000
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Senior Member |
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Declan Vogt wrote:
> I'd like to find out what IDL will use as the max and min values for a
> graph axis before it actually plots the axis. I've been doing this by
> creating a window, drawing the axis, and reading !x.crange, then erasing
> the window, but it's not very elegant, and it doesn't work for
> postscript.
>
> Does anyone know if there is an IDL routine I can call?
I don't think there's a built-in routine for this purpose. However you can
always use the Z buffer as a temporary graphics device:
Say your data is defined as follows:
x = findgen(200) * 0.1
y = sin(x)
First you save the current graphics setup:
entry_device = !d.name
entry_window = !d.window
entry_config = {x:!x, y:!y, z:!z, map:!map}
Then you create a temporary plot in the Z buffer:
set_plot, 'Z'
device, z_buffer=0
plot, x, y, /nodata, xstyle=4, ystyle=4, /noerase, /ynozero
xrange = !x.crange
yrange = !y.crange
Then you restore the entry graphics setup:
set_plot, entry_device
if (entry_window ge 0) then wset, entry_window
!x = entry_config.x
!y = entry_config.y
!z = entry_config.z
!map = entry_config.map
The x and y axis ranges computed by IDL are then returned:
print, xrange, yrange
0.00000 20.0000
-1.00000 1.00000
This method does not require a graphics window to be open, does not care
what graphics device is active, does not disturb the contents of the Z
buffer, and does not disturb the current plot settings.
Cheers,
Liam.
http://cimss.ssec.wisc.edu/~gumley
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