[R] Normal score transform of spatial data
Michael Grant
mwgrant2001 at yahoo.com
Fri Jul 28 21:02:51 CEST 2006
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
>
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