topic standard deviation in Spatial Statistics Questions

standard deviation

HannahTarling — Wed, 19 Apr 2017 21:16:49 GMT

Hi, I have classified and visualized a field in a vector data set according to standard deviation. I am also wanting to put the standard deviation values into a histogram so I can compare standardized results with another data set. Does anyone know how standard deviation values can be derived and made a field? Thank you!

Software: Arc Map 10.4

Re: standard deviation

DanPatterson_Retired — Wed, 19 Apr 2017 22:49:39 GMT

Summary statistics is one option

Re: standard deviation

curtvprice — Thu, 20 Apr 2017 01:26:37 GMT

Hannah, It sounds like what you are looking for is normalized data, that is, Z-scores for every data value. The Z score expresses your data field as number of standard deviations from the mean (negative less than mean, positive greater than mean). Z-scores are often used for just that purpose -- comparing the shape of distributions of two datasets that have different means and standard deviations.

The easiest way in ArcMap would be to add a field of type Float (let's call it "ZSCORE"), right-click the data field you were mapping and selecting Statistics, copying the mean and stdev value from the popup, and then running Calculate Field on your ZSCORE field with the expression:

(!DATAFIELD! - mean) / stdev‍‍

(For VB syntax, that would be [DATAFIELD], but I recommend going with Python.)