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Is there any option how to do a Spatial Analyst tool "Look up" operation from ArcGIS 10 in ArcView 3.2? I have a grid with attributes and need to "extract" values from the table field (values from 0.75 till 1.38) to make a floating-point grid with these values.

I am a beginner in ArcView SW, have not so much experiences. I have tried a reclassify, map calculator, but with no success. Is there some way out how to do it in ArcView 3.2 (Spatial Analyst v2.0a)?

Thanks in advance for any help.

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Could you please explain what you're trying to accomplish? Does this question refer to (a) selecting cells by value, (b) referencing attribute fields other than the default [Value] field, (c) conversion from integer to floating point format, or (d) something else? –  whuber Feb 13 '12 at 18:49
    
It refers to (b) and (c). I've done by one way now, but I'm not sure, if it's correct procedure. I made a new Field > calculate values *100 to avoid decimal mark. Then I reclass and use Lookup option with this new Field. Then I use Map calculator and calculate ([Layer].Float) / 100. I apologize for my English. –  davidmrnustik Feb 13 '12 at 19:51

1 Answer 1

up vote 1 down vote accepted

In the Map Calculator use an expression like

[My grid . Count].Float

"My grid" is the name of an integer grid and "Count" is the name of a field in its attribute table. A single space on each side of the "." is essential. It's best not to type this yourself: you can find a list of all such grid+field combinations displayed within the Map Calculator dialog. Double-click on the one you want. This copies its name into the input textbox. Then type the ".Float" part directly.

You can create extended Map Calculator expressions if you like, as in

[My grid . Count].Float / 100.0

Be careful, though: the syntax is not entirely documented; it is strange; and it is finicky. (It seems nothing has really changed over the last 20 years except for the details. :-) For example, "100." will not work; you need to write "100.0". As another example, if you fail to include ".Float", ArcView will perform integer arithmetic, even though "100.0" is explicitly floating point. Therefore, it's usually best to do just one thing in each Map Calculator expression, checking the results carefully after each step. To make it possible to reproduce your work later, I recommend copying and pasting the MC expressions either into a Script Editor document or into the "comments" field of the grid theme's "Theme Properties" dialog as you go along. Save your work early and often, too... .

For a complete list of things you can do with grids in the Map Calculator, see the help page for "Grid (class)".

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Thank you very much for comprehensive answer whuber. That's exactly what I was trying to accomplish. Very useful informations as well, I did't know about ".", 100.0 and not typing manual. Good tip for copying and pasting the MC expressions into comments. And I've already learned saving work early and often during working with ArcView 3.2 :) –  davidmrnustik Feb 14 '12 at 8:14

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