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Hi Eric,
I was searching to know how exactly the (ArcGIS) software back-transforms log-normalized data into the original scale. I am particularly interested in how this is handled in EBK, in case it's handled differently in other models. Please, can you explain to the extent possible?
Thanks
Elijah
I don't know of any direct way to compute the sill of the untransformed data from the sill of transformed data (other than just not transforming and calculating it). But I'm not clear on why you want to do this. The software models the semivariogram in the transformed space, but it does the back transformation automatically. The resulting surface will be will be in the original untransformed units.
You need to understand a few things. By applying a log transformation in kriging, you're saying that the logarithm of the data values follows a Gaussian spatial process whose covariance structure can be modeled with a semivariogram. This doesn't necessarily imply that the untransformed values can be correctly modeled with a semivariogram. In this case, it only really makes sense to talk about correlations, sills, nuggets, etc of the log-transformed data. If you want to try to make these statements about the untransformed data, you need to try to model the data without a transformation. But again, this may not be possible, depending on your data.