Re: [R] Normal score transform of spatial data

From: Michael Grant <mwgrant2001_at_yahoo.com>
Date: Sat 29 Jul 2006 - 05:02:51 EST

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

> 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
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>
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>
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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. Received on Sat Jul 29 05:10:48 2006

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