Normal score transform of spatial data
Hi Tom, I do not know about R but you might take a look at the GSLIB codes. It has executables for both tasks using a simplfied GEOEAS format. I recently did some Normal Score Kriging and use a combination of GSLIB, GEOEAS, and R (for the contouring of the resulting grid). BTW I used GEOEAS instead of one of the R packages because of the way the distance in each lag is calculated. I have not explored the matter but my impression is some codes/packages use the mid-point of each lag interval and some use the average pair distance for the interval...need to look at that sometime [Moral: use packages with caution--not because of any inherent flaw but because of differences in approach. You need to know what is being done.] Regards, Michael Grant
--- Thomas Adams <Thomas.Adams at noaa.gov> wrote:
List: I have 2 related questions: (1) first I have x-y-z data, where x & y are the geographic locations of point values, z. I need to perform a normal score transform on the z-values and maintain their geographic location. So, how do I go from columns x-y-z to x-y-z-t (or x-y-t), where the t-values are the normal score transforms of the z-values? Can I use qnorm(ppoints(data)) to do this; how? (2) I also need to do a reverse transform of a matrix of normal score values (v) to my original data value units; I have seen that I can use something like approx(t, x, v)$y. Again, the matrix represents a spatial grid. So, how do I maintain the same spatial ordering resulting from the reverse transform? Thank you for your help. Regards, Tom -- Thomas E Adams National Weather Service Ohio River Forecast Center 1901 South State Route 134 Wilmington, OH 45177 EMAIL: thomas.adams at noaa.gov VOICE: 937-383-0528 FAX: 937-383-0033
______________________________________________ R-help at stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.