| Re: IDLgrAxis expanding [message #15056 is a reply to message #15055] |
Wed, 14 April 1999 00:00   |
davidf
Messages: 2866
Registered: September 1996
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Senior Member |
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About a half hour ago I wrote this in response to a question
by Pavel Romashkin:
>> When an instance of IDLgrAxis is created without /EXACT keyword, it is
>> adjusted by IDL so that tick labels are nicely rounded. However, this
>> has a side effect of non-/EXACT axis extending past the limit of the
>> VIEWPLANE_RECTANGLE for the parent IDLgrView. Sometimes this expansion
>> is really large. Is there a way to make IDLgrAxis to round ticks but
>> lie inside the VIEWPLANE_RECTANGLE?
>
> If there is a way, it must be undocumented. :-(
Just after I finished this article (it being rather late) I said
to myself, "The hell with it, I'm going to have a beer". Of course,
I was out of beer. So on the drive to the liquor store the solution
came to me. :-)
I reasoned this way. *Someone* has to know the actual range of
the data, since it clearly gets drawn. Who is it who knows and
how can I get at that information? Using my best Sherlock
impersonation, I finally realized that it is the text object
that creates the labels that knows how long the axis is. So
how do I get at the labels? Humm. The STRINGS keyword! OK.
So here is how it is done. (It's a bit convoluted here,
but it's a solution programmers will love.) I'm showing
here just the calculations for the dependent data axis,
but the other axes will be done in the same way:
************************************************************
; Get the range of the data.
thisPlot->GetProperty, XRange=xrange, YRange=yrange
; Set up the scaling so that the axes for the plot and the
; plot data extends from 0->1 in the X and Y directions.
xs = Normalize(xrange)
ys = Normalize(yrange)
; Create the Y axis.
yAxis1 = Obj_New("IDLgrAxis", 1, Color=[255,255,0], Ticklen=0.025, $
Minor=4, Title=ytitle, Range=yrange, YCoord_conv=ys, $
Location=[0, 1000, 0])
; Get the text object containing the labels.
yAxis1->GetProperty, Ticktext=yAxisText
; Get the strings.
yAxisText->GetProperty, Strings=theseStrings
; Find the first and last of these strings. This is the REAL
; axis range.
nstrings = N_Elements(theseStrings)
minRange = Float(theseStrings[0])
maxRange = Float(theseStrings[nstrings-1])
newRange = [minRange, maxRange]
; Set the axis range to the REAL range.
yAxis1->SetProperty, Range=newRange
; Find new scaling values for this REAL range.
newYs = Normalize([minrange, maxrange])
; Re-scale both the axis AND the data into this new range.
yAxis1->SetProperty, Range=newRange, YCoord_Conv=newYs
thisPlot->SetProperty, YCoord_Conv=newYs
************************************************************
Works real good on my example program, even if it *is* a
bit of a hack. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155
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