Working with a routine process today that I normally only do once in awhile but today needed to do it several times. It requires changing the definition query on several features classes. Being the ‘lazy’ GIS guy that I am (owner of a company I used to work at called me that once as a sort of compliment for my tendency to script a lot of what I did), I decided to finally script it instead of changing definition queries about 42 times.

Recently we took a call from a user who could not see the legend for one of the feature classes in one of our services. (Precambrian Bedrock in http://mgsweb2.mngs.umn.edu/arcgis/services/state/mnbdrkgeology ) After trying some standard things–restarting the service, checking the source .MXD–I turned to The Google Machine and quickly found help from ESRI: http://support.esri.com/zh-cn/knowledgebase/techarticles/detail/33741 . Turns out the default number of legend items ArcMap will display from an ArcGIS Server map service layer is 100 and we had 102 in the problematic layer.

In the last week, I have looked for multi-part features a couple of times. Today, I was looking for multi-part polygons after dealing with the fall-out of a case of Clip Gone Wild as shown below. I have not found a way to write a query to find these but Field Calculator does allow you to calculate a field’s value to the number of parts. Using the Python parser, just write the formula (note that case matters): !

I’ve found that sometimes I can not find the answer to a question until I know the answer & then it becomes ridiculously easy to find the answer. One small annoying thing that I never spent much time was when you delete features from a feature class making it significantly smaller but the envelope does not get re-sized so the zoom extent (still the original extent) is too large. This often happens to use when we convert tables to an XY theme and there are blank records–most of our data shows in Minnesota but there are some in Oklahoma (I think).

Seems like a lot of people are finding the ArcMap Field Calculator examples that I have posted useful so I will make an effort to post more of them. Most posts are generated after I do something and think that others might want to know how to do it. (Or so I can go back and remember how I did something without re-inventing it). Something I did today was create a field (!

You may have noticed that this post–ArcMap Field Calculator: Identifying Unique Cases, Single Field–specifies ‘Single Field’. Yes, that was my version of a cliff-hanger post. The basic structure I listed in that post can be expanded on to satisfy your needs. The example in my earlier post was case sensitive for example, you could modify it so it treats ‘a’ the same as ‘A’. Today’s example groups records into different cases based off the values of two fields, !

Apparently, if you post one time about ArcMap field calculator, you’re bound to get additional questions. After my recent post about using field calculator to convert text values to numeric, someone asked about a problem they were having with another calculation they were having. The underlying problem was that python 2.6, which is installed with ArcGIS 10, uses integer division when both the numerator and denominator are integers. The result of integer division is an integer rounded towards negative infinity.

Received a request yesterday asking how to use the ArcMap Calculator to copy values from a Text field to a Double field using python syntax. As any good blogger would do, I immediately thought, ‘Awesome! Someone’s question is the perfect topic for a new blog post’. The python parser is actually pretty good at casting values on the fly so if the values in your text field (!Day! in my example) are valid values that can be converted to a Double value, it is as simple as just setting the formula to be the text field.

One of the standards in our databases is to store dates as 8-digit integer values in the format of yyyymmdd. This requires us to occasionally convert values from date fields into this format. We can do this in the ArcMap Field Calculator using this arcpy function: def datetodouble(inNum): splitList = str(inNum).split("/") return splitList [2] +("0"+ splitList [0])[-2:] +("0"+ splitList [1])[-2:]

One of the common functions I have to do is assign each record in a feature class with a unique identifier–normally just a sequential number from 1 to N. In ArcView 3.x, the formula was simply ‘rec + 1’ if I wanted to start with the number 1. In ArcGIS, the process got a little more complex–you had to write a little VBA in Field Calculator as described by ESRI.