standard deviation

HannahTarling

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

curtvprice

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:

<SPAN class="punctuation token">(</SPAN>!DATAFIELD! <SPAN class="operator token">-</SPAN> mean<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">/</SPAN> stdev‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN></SPAN>

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