[GIS] Calculating Mean for Multiple Rows in ArcGIS for Desktop

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I am trying to calculate a mean across a multiple number of attribute rows and have this value added to a new field that I have entered in the attribute table. I have an attribute table which has a number of different ecoregion types associated with them.

For example:

If I select "Arid Canyonlands" there are 3 attribute rows that are selected, each with their own "mean". I am trying to add a new field to the attribute table which will take the "mean" of these three and populate that value in the new field created. I could manually do it through an editing session and using a calculator but just wanted to know if there is an easier way to actually do it through field calculator?

Best Answer

I think you should use the Summary Statistics tool to calculate the mean:

Calculates summary statistics for field(s) in a table.

...

The following statistical operations are available with this tool: Sum, Mean, Maximum, Minimum, Range, Standard Deviation, Count, First, and Last. The Median operation is not available.

Your "ecoregion type" field would be used as a case field:

If a Case field is specified, statistics will be calculated separately for each unique attribute value. The Output Table will contain only one record if no Case field is specified. If one is specified, there will be one record for each Case field value.

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1 square metre is 10.7639104 square feet according to Google.

Therefore if the cell size is 1 each cell is 1 square metre (1 x 1), the area covered by class is:

Count x 10.7639104

if the cell size is 2 metres the area is 4 sq.m. (2 x 2) and the area covered by class is:

4 x Count x 10.7639104

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[GIS] Using if else statement in Python Parser of Field Calculator in ArcGIS for Desktop

The problem is in your code block.

Instead of:

def Reclass( !CODE! , !COMPLEX! ):
    if ( !CODE! == 1.1.7 and !COMPLEX! == 4):
        return 1.3
    elif ( !CODE! == 3.2.0 and !COMPLEX! == 4):
        return 1.3    
    else:
        return 0

try:

def Reclass( CODE , COMPLEX ):
    if ( CODE == "1.1.7" and COMPLEX == 4):
        return 1.3
    elif ( CODE == "3.2.0" and COMPLEX == 4):
        return 1.3    
    else:
        return 0

The exclamation marks are needed in your expression because there they are indicating field names but in the code block CODE and COMPLEX are Python variables and could be called a and b if you wanted.

The other problem is that your CODE field appears to be of type text so I have added quotes around the tests of its values. I cannot tell if your Map1 and COMPLEX fields are text or numbers so I have not put them there - you may need to!

Best Answer

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[GIS] Using if else statement in Python Parser of Field Calculator in ArcGIS for Desktop

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