Tagged Questions

The Field calculator in ArcGIS-related products can recalculate the values of a single field on all or selected records within a table based on a symbolic expression in a programming language.

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6
votes
2answers
2k views

Basic Field Calculator Python Question

I'm trying to used the Python syntax in ArcGIS 10's field calculator and am thoroughly confused. So far the most basic calculations are failing me, and I don't understand why. I'm trying to create a ...
7
votes
7answers
906 views

How to Remove return/newline (\n) character from Field using Python and Field Calculator?

I have a geodatabase table with a field that I'm trying to remove return characters (new line). I found this post (How can I remove (chomp) a newline in Python?) of how to do it, however it is not ...
3
votes
3answers
193 views

Auto-calculate field (area or formula)

I'm wondering if anyone has any insight into the potential to auto-calculate the value of a field, either area or distance (ideally) or a formula (based on the values of say 2 other fields, or an ...
10
votes
2answers
534 views

How to compute a new attribute based on changes in another attribute?

I am attempting to classify a set of gps time-encoded point data into behaviors based on different attributes. I have created an attribute that is 0 for home and 1 for away based on location, and now ...
5
votes
4answers
4k views

How do you test for a NULL string field in the Field Calculator with Python?

I am trying to perform an operation on a string field with a condition that it contains data. Referencing None with Python does not appear to work when the field is nullable and contains <Null> ...
1
vote
1answer
133 views

Why does Field Calculator return 0 values when decimals are expected?

I realize I posed this question, and got answers, several days ago (see (Field calculator error)) , but none seem to really be working, and so am posing again. Below are two screenshots that show the ...
1
vote
1answer
872 views

Do QGIS Field Calculator xat(n) and yat(n) functions work in version 1.7.x?

I'm trying to use the xat(n) and yat(n) in the Field Calculator but can't get them to work. Does anybody have an example how to use them? I need the start and end coordinates for line segments, does ...
0
votes
2answers
699 views

Update NULL values MDB table

How do you update NULL values within mdb geodatabase table using ArcGIS Field Calculator (service pack 4) without changing other values to NULL? I've tried the suggestions on this previous question: ...
3
votes
3answers
132 views

Field calculator error [duplicate]

NOTE: This problem is similar to one that was answered here: Why does Field Calculator return 0 values when decimals are expected? I'm relatively new to python, and am trying to run a simple field ...
3
votes
1answer
158 views

Is there a (better) way to debug Visual Basic Code Block in calculate field using ArcGIS?

From time to time, I have to use Visual Basic in Calculate field. As the code get bigger, the more complicated is to debug it. And ArcGIS (9.3) does not help as the error messages are, in the best ...
2
votes
1answer
400 views

Iterative position within Field Calculator/Python

I'm not great with Python or programming in general, so I'm not even sure how to ask this question. Basically what I've got is in the left column, and what I want is in the right column. UniqueID ...
6
votes
2answers
581 views

Calculating Field based on name of shapefile

I have multiple shapefiles to which I have added a field called "gname1". For each shapefile, I want "gname1" to be set to the name of that particular shapefile, for every feature within the ...
5
votes
1answer
1k views

Python Field Calculator ArcGIS 10 expression for a RANGE

what is the python expression for defining a range of numbers? I have tried numerous combinations but cannot get a simple range of angles (100 -200) to compute correctly. Screen shot : screen shot ...
5
votes
1answer
730 views

Get shape filename in attribute field using field calculator

I apologize for crossposting against the ESRI geoprocessing forum, but it seems like this one gets answers. I'd like to have a modified append tool (ArcToolbox) that takes multiple shapefiles with ...
4
votes
3answers
2k views

ArcGIS 10 Python split string

I am trying to use Python to split a string field into three new fields at the separator " - ". The field is in the format "a - b - c". So I initially had this in the field calculator for newFieldA: ...
3
votes
2answers
2k views

Using conditional statements in Field Calculator

I have two fields, "P_Area" and "PC_Area", whose sizes I'd like to compare in a third field, "Areas_Equal". The "Areas_Equal" field should contain a "Yes" if the other two are equal and a "No" if they ...
3
votes
2answers
2k views

Nested “if” statements in ArcGIS Field Calculator

The solution in VB for the base process is @ "If then" VB Script code (or Python) equivalent to SQL's IN ('x','y',z') expression in ArcGIS Field Calculator question? ...
5
votes
2answers
93 views

Using field calculator to delete specific contours

I have 3 contour shapefiles with 25m, 50m and 100m equidistance. Now I want to delete in the 25m-shp-file every **50m and **00m contour and in the 50m-shp-file every **00 contour. How can I show them ...
5
votes
1answer
380 views

How to fill my column with consecutive numbers

I m very new to Qgis, so forgive this simple question. Searching in older topics didn t help either.So: I make a new column in my attribute table and it has a default value(for example 0). I want to ...
5
votes
2answers
2k views

Using Field Calculator in QGIS to update columns with centroid coordinates

In QGIS I would like to update two columns with the centroid easting and northing of my polygons. I am using the field calculator. I have tried using $x and $y but this only seems to work for points. ...
4
votes
4answers
127 views

How do I fill in serial letters (AA, AB,AC…,BA,BB,BC…ZZ) to a shape?

(I am using ArcGIS software, ArcMap...) MY PROBLEM I have a shape file containing points. The shape file contains 3 columns named FID, Shape* and Label. In the column I want to fill in AA, AB, ...
4
votes
1answer
2k views

Find and Replace expression needed in Field Calculator ArcGIS 10

Looking for the Field Calculator code (Python preferred) to replace the last numeral values in a field using another field's values for entire attribute table. Please see screen shot here:
2
votes
1answer
137 views

Am I over-complicating adding and then calculating fields? Suggestions for a better way? (Python)

I'm attempting to re-position a question I asked yesterday here. I am starting to think that the way I wrote my code just isn't the best way. Am I overcomplicating things? I know for a fact that ...
2
votes
1answer
99 views

Incorrect field name resulted in RuntimeError: ERROR 999999 (Also, better code for adding and calculating fields)

This is the bottom half of my code (and it's been edited somewhat to share publicly). The code works perfectly fine when the fieldList has only three fields in it, but when I populate it with all 108 ...
2
votes
1answer
150 views

Unit of $length in QGis Field Calculator

I'm calculating field of various features in my shapefile using QGis. I'm getting some sample length as 0.134914579766986. I want to know in what unit (eg: meters, km etc) is the above value ?
2
votes
1answer
215 views

Counting occurrences across a record in ArcGIS 10.0

I'm a student at Millersville University, PA studying for a BA in Geography with a concentration in GIS. I've stumbled across this site for questions I've had over the past year or so with getting ...
2
votes
1answer
319 views

Field Calculator operation is not working

I've done this 100s of times and I can't understand why it won't work! I'm trying to copy the first 8 digits of from a HUC 12 (Hydrologic Unit Code) to a new field, which represents a larger ...
2
votes
1answer
989 views

How to set the value of a field in all selected rows of a table using ArcGIS 10

I have an attribute table in ArcGIS (it's large - around 300,000 elements). I've selected some rows of the table using 'Select by attributes' and I want to set the value of a field for all of those ...