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Last Post 19 Nov 2010 11:44 AM by anon

IMAGE function and /YLOG

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anon

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19 Nov 2010 11:44 AM
Hi folks, The new IMAGE function has an option to choose logarithmic axes (i.e., YLOG=1) but I have yet to get it to work. When /YLOG is set, the yaxis will be compressed into a very short line (i.e., the entire image becomes "squashed"). I've made sure no y-axis values contain 0, etc., and also tried using ASPECT_RATIO = some # to try and force it to a more usable shape...to no avail. The application here is plotting a frequency-time power spectrogram with a log frequency scale on the y-axis. I have a routine that does this successfully...and there are others on the web...but they all use acrobatics with the TV routines to get this done, whereas using the IMAGE function would be easier (and enable more functionality) if it can be made to work. I'd be curious if anyone has used /YLOG with IMAGE under any circumstances that works...right now it looks basically non-functional to me.

MariM

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22 Nov 2010 01:28 PM
Do you have the IDL 8.01 patch? You can download it from this website.

Deleted User

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23 Nov 2010 09:38 AM
I did indeed eagerly install the latest patch - and in fact that fixed another problem with YLOG and the new PLOT function (which caused the title to move to an odd place). However the behavior of IMAGE and YLOG was unchanged. I also tried to use YLOG with the old IIMAGE itools routine and saw a similar problem. Ideally the IMAGE function would just YLOG the yaxis (or x, for that matter) and let you display whatever image you wanted to within the axes (i.e., using AXIS_STYLE=2). Either it's trying to perform some transformation on the image, or something else is wrong ... in any case, most attempts yield an infinitely small physical dimension for the yaxis when YLOG is set. Using really high aspect ratios (ASPECT = 200!) yields a more realistic plot box, but the image within then looks wrong...either transformed beyond recognition or only a small subset of the original image is visible (I can't tell which). In any case, still interested if anyone has gotten YLOG to work with IMAGE under any circumstances, it would be great to see an example.

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