VBScript If/Then Statement – How to Use If/Then Statement in VBScript for ArcGIS Field Calculator

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I am trying to do a simple (or so I thought) if/then statement in the ArcGIS field calculator.

I am trying to add the HydroCode field – hydologic soil codes – to an existing data set. I know what the code should be based on the "MUSYM" number. For example, "MUSYM" 1667 has the hydrologic soil code A. The "MUSYM" field is a number and the "HydroCode" field is text.

I vaguely remember doing if/then statements years ago when I more actively used GIS. I have tried simple If "MUSYM" = 1667 Then "HydroCode" = A Endif along with some other variations but none are working.

What am I missing?? All of the help I have found online deals with very complex coding, I can't find anything for such a simple statement. I also can't find anything with just basic operational instructions as far as where the operators should go/punctuation/etc.

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Best Answer

Normally, I try to direct anyone using the Field Calculator to use Python. But to answer your question directly, you'll need something similar to this below. It's a basic pattern of if/elseif/end if.

(substitute your own values of course, I use 9999/Z just to show an elseif)

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Note: You mention that MUSYM is a number, but the way the values in your table are aligned to the left makes me think it is stored as a text field. If so, try the below instead:

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[GIS] Writing If-Then Statement in ArcGIS Field Calculator using Python Parser

Using Python, the calculation would look like this:

For the Pre-Logic Script:

def Calc(a,b,c):
 if a == "000":
      return b
 else:
      return c

For the expression:

Calc( !A! , !B! , !C! )

ArcGIS Desktop – Using If/Then Statement with LIKE in Field Calculator

There is no LIKE comparison operator in VB Script (see link).

You could use InStr to check if some search text appears somewhere in the input string:

dim y

If InStr([Categories], "Orange") Then
  y = "Medium"
Else
  y = [Categories] 
End If

Status = y

InStr will return 0 if the search text is not found, which will be interpreted as False in the condition statement.

If you want to search some text explicitly in the begining of the input string, just check if the value returned from InStr is 1.

If you want to search some text in the end of the input string, try Right function to extract part of the string and then do the comparison.

Best Answer

Related Solutions

[GIS] Writing If-Then Statement in ArcGIS Field Calculator using Python Parser

ArcGIS Desktop – Using If/Then Statement with LIKE in Field Calculator

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