[GIS] Setting Zero values back to NULL

arcgis-10.2arcgis-desktopfield-calculator

I'm working with ArcGIS 10.2 for Desktop and OS Windows 7.

I need to set numeric vales from Zero back to NULL, but I can't from the field calculator.

I'm working with a vector file and I need to display NULL in one column that shows 0 (Zero) as default value.

——– Edit——-
I am adding the error messages that he received
Error Message 1
Translation: An error occurred during the process. Please consult the Geoprocessing Results Window to obtain more details.

Error at bottom, translation: The values of the selected column can not be set to null because the field in the database is defined as "Not Null".

Best Answer

Assuming you are using ArcGIS, and not QGIS, this is a simple operation. It definitely can be performed in the Field Calculator. I created a field, "test_num", type of Double as an example. This is in ArcGIS 10.2 on Windows 7, 64bit.

Source Table - Data set to 0 Source Data

Field Calculator: Simply enter NULL as the value to be calculated. Field Calculator - NULL

Result Table - Selected values are now <Null> Result Table - Values set to NULL

--------- Edit -----------
Based on the additional screenshots you provided, the issue is clear. You cannot set the values to NULL because you have specified that this column Cannot have NULL values.

Your best bet is to create another column that allows Nulls, and try this operation again. If you are still finding an error, please modify your question with additional information.

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You probably have a divide-by-zero error. Field Calculator definitely cannot divide when zero is the denominator, and sometimes will even throw errors with zero as the numerator. To get around this, click the "Select by attributes" button in the Attribute Table (top left corner, third from the left). Then type in this formula:

"Asian" <> 0 AND "Total" <> 0

This will select only records with no zeroes. When you use field calculator, it will only process these records. You can play around with other selections to get it right.

ArcGIS Pro – Fixing Calculate Field WARNING 002858

Edited to reflect @Vince's comment which is correct. Firstly, you need to pass the gop and dem votes into the function. Also, you're trying to return a string in your function but haven't enclosed it in quotes.

Try the following:

def Reclass(votes_gop, votes_dem):
    if (votes_gop > votes_dem):
        return "Trump"
    elif (votes_dem > votes_gop):
        return "Clinton"

further, for completeness, you may want to add the case when votes are equal.

def Reclass(votes_gop, votes_dem):
        if (votes_gop > votes_dem):
            return "Trump"
        elif (votes_dem > votes_gop):
            return "Clinton"
        else:
            return "Tie"

Also, this assumes you have valid values for all records in the votes_gop and votes_dem fields. If any of them are Null, you may run into problems.

Also, I just noticed that you're first line has Wnner instead of Winner.

Invocation of the function should be:

Reclass(!votes_gop!,!votes_dem!)

Best Answer

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