Log transformation in ArcGIS 10

Discussion created by eiffel8 on Aug 12, 2011
Latest reply on Aug 17, 2011 by eiffel8
Dear experts and valued members,

I am doing OLS and cant come up with a better model. I found out that some of my variables need transformation however, I can't figure out the right transformation of my explanatory variables as I am not that well verse in stat. I have attached the screenshot of what I did in ArcGIS 10.

Explanatory variables: DEM and MAR (mean annual rain)
Log transformed Field: demtra and lograin

Formula: Demtra = Log ([DEM])
Formula: MAR = = Log ([MAR])

Demtra = Log ([DEM]) (result is highlighted in light blue). I did the same calculation in Excel, when I used the Log function in excel I got different results. I tried LN (natural logarithm) in Excel and got the same result as Log ([DEM]) in ArcGIS. I am wondering if I am doing the right transformation using the above formula when there is a need to transform the data to logarithm. The DEM variable is skewed to the right as such I am doing log transformation.

I did the same transformation for MAR (mean annual rainfall) and the Lograin (last column)  resulted to single values though I indicated a precision of 2 when I added a new field.

I would appreciate any assistance on this. Thank you so much for your valuable comments and time in helping out.