MathGroup Archive 2002

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Miscellaneous questions

  • To: mathgroup at
  • Subject: [mg36785] Miscellaneous questions
  • From: "Steve Gray" <stevebg at>
  • Date: Wed, 25 Sep 2002 01:51:10 -0400 (EDT)
  • Sender: owner-wri-mathgroup at

I would appreciate any info on these issues.

1. I have a symbol "slback." I was getting
"tag times lback protected " (or something) errors.
(A typically uninformative error message.)
I suspected there was a separation between the s
and l, and they looked too far apart, but when I
spaced past them with the arrow keys, there did
not appear to be anything like a space in between.
I retyped the symbol and all was ok. This has
happened before. What's going on ???

2. I'm using Raster to plot data points
in a 256x256 array. Two problems: First,
regardless of the ImageSize setting (I need the
display as big as possible), the individual data cells
when examined closely at 300% vary in size by
almost 2:1. This makes detailed inspection of the
data values difficult. Surely there is some setting
of something which would make each data cell an
exact number of screen pixels? Second, I'm
Show[ Graphics[Raster[ rescol,
                          ColorFunction -> Hue]],
                          AspectRatio -> Automatic,
                          ImageSize -> 700];
but the Hues don't allow enough easily distinguishable
shades to visually recognize even 6 data values easily.
(I'm slightly colorblind.) It would be nice to have black
and white available for two of the data values, but Hue
does not allow this. I don't understand what the
documentation says about RasterArray.

3. I wanted to get this raster image into a format
where I could dissect it with Photoshop or equivalent.
After much fooling around, I found that I can export the
selection as an html file, read it into Navigator, do File>
Edit Page, which brings up Netscape Composer, right
click the image which, allows saving it as a GIF, which
I can finally work on with a photo editor. Maybe
there is an easier way, or maybe this description will
help someone with the same need.

    Thank you for any answers!

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