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I have a Excel file showing annual precipitation and I add it on arcmap. When I tried to check it's attribute table the field calculator is passive. I want to change all the Null value to specific number for analysis. how can i solve it plz.

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Excel data cannot be edited using ArcMap. It sounds like you may have added it to ArcMap as an XY Event Layer so from there you could Export to Shapefile or Feature Class and then use the Field Calculator. –  PolyGeo Mar 22 '13 at 1:12
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4 Answers

If your data is an Excel table to start with, you can do a global search and replace in Excel before importing to ArcGIS.

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Thank you PolyGeo, I luv your answer –  user16377 Mar 23 '13 at 5:13
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Try this method :

  1. Import your Excel sheet to ArcMAp
  2. Export the sheet to dbf
  3. Go to table properties of dbf
  4. select Definition query => click Query Builder
  5. Select the field with Null values then Click "Is" Button
  6. Click "Get Unique Values and select Null
  7. Now you can use Field Calculator to change Null.

sample : "City" IS NULL

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if you import it to a gdb you can run calcField like so

  1. open the Calculate Field tool
  2. set the input table, field name (your date field), expression type to PYTHON
  3. set the expression to

  4. put this code into the code block (update my dec 31 1981 to your desired date)

    import datetime
    def x(v):
    if v is None:
      return datetime.datetime(1981, 12, 31)
      return v
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If you want to be able to edit the file directly in ArcMap, you can also save your .xls as a .dbf before importing it.

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Please explain how and/or that would help solve the problem described in the question. –  lynxlynxlynx Apr 21 '13 at 10:11
The older versions of Excel (maybe 2003?) allowed save as.. with .dbf , but not the newer versions. I use open office Calc rather than Excel for that reason. Also there's Libre (office?) Calc that does the same. Whenever you do this, be careful about the field being either string or number (and formatted to the digits you need) because the resulting .dbf imports those fields' formats and that's always what trips me up. –  Geocurious Apr 22 '13 at 1:39
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