# What Classification Method; how many Classes; what class ranges; what Break Values – set for my each single feature class?

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11-19-2017 01:50 AM
New Contributor

Hey everybody!

My name is Gregory and I’m an ArcMap newbie. I have two feature classes. One feature class for certain year. Second feature class also for certain year, but not for same year as in first feature class.  Type of features stored in these two feature classes is Polygon Features. These Polygon Features are counties located in certain country. Each single feature class displays in Canvas / Map Display Window / Display Area only these counties located in the certain country, in which dead creatures (as a result of the certain disease) have been confirmed. Attribute table of each feature class contains a column creaturesDeaths, in which cells there is number of dead creatures in given county. Each single feature class I want to represent on choropleth map, in which values (number of dead creatures) are referenced to counties. Because attribute table of each single feature class have a large number of rows, I made frequency statistics for the attribute table of each single feature class. Frequency statistics works as follows: Reads a table and set of fields and creates new table containing unique field values and the number of occurrences of each unique field value.

Attribute table of each single feature class - The attribute tables containing the field that was used to calculate frequency statistics.

creaturesDeaths - The attribute field that was used to calculate frequency statistics. Column creaturesDeaths is in attribute table of each single feature class.

Now the question. What Classification Method; How many Classes; What class Ranges; What Break Values – set for each single feature class?

I want to make a choropleth map from each single feature class. Not from each single output table (Data_Year1_Frequency, Data_Year2_Frequency) from frequency statistics.

For example, Look at the picture of first output table from frequency statistics -    Data_Year1_Frequency.jpg

Look at the first row.  There is value 16 in the field FREQUENCY, and value 1 in the field creaturesDeaths. It means that in attribute table of first feature class there are 16 rows that have a value 1 in the field creaturesDeaths (= In each of 16 counties died 1 creature).

I'm sorry if I repeated my sentences too many times. I will be grateful  if someone help me. This is  the beginning of my adventure with ArcMap. If my knowledge of ArcMap will increase, I will help others as someone help me now.

Greg

4 Replies
MVP Esteemed Contributor

Compare the histograms under the symbology Classify link or actually get the histogram from your count data.  That will tell you whether the distributions are the same or different.  Since you are working with count/frequency data, there is nothing wrong with doing a manual classification as a start.

Just looking at the table, your locations have produced highly skewed data to begin with.  What are the means and standard deviations to begin with?  There is a big switch between the high obviously, but at the low end, there is a change in places recording 1.

Manual graphing using manual ranges refining as you go along will help until you can get a sense whether the pattern between the tails of the distributions have remained the same.  And in short,  there is no 'one' appropriate method, there may be one that is more suitable once you have examined the distributions and capture the method that reflects both sets of data for both times.

New Contributor

I prepared 2 PDF files. Each single PDF file contains informations about another yearly feature class.
Each single PDF file contains – histograms, Mean, Standard Deviation and another informations.

MVP Esteemed Contributor

Good, so you have a starting point from which to make your decision on what to actually use in coming up with the type of classifier and its parameters.

New Contributor III

I agree with Dan you can look at the histograms and that might be all you need but if you wanted to calculate the frequencies you could also use the statistics drop down and run some analysis. If you created a new field you could sort by/create additional maps with this new information.