Gaussian transformation
Thank you for your answers. In the meantime, I found the package RGeostats developed by Geosciences Research Center of MINES ParisTech on http://rgeostats.free.fr and at the moment I'm studying it. It seems promising with 3D geostatistics capability and function for gaussian anamorphosis transformation and back transformation. Carlo 2015-04-29 15:11 GMT+02:00 Paulo Justiniano Ribeiro Jr < paulojus at c3sl.ufpr.br>:
Perhaps you can also look at the Box-Cox family of transformation for
which some cases such as log is a particular case You may look at MASS::boxcox() and/or boxcox related functions in geoR If log works well you benefit from the results of log-normal kriging.
Paulo Justiniano Ribeiro Jr LEG (Laboratorio de Estatistica e Geoinformacao) Universidade Federal do Parana Caixa Postal 19.081 CEP 81.531-990 Curitiba, PR - Brasil Tel: (+55) 41 3361 3573 VOIP: (+55) (41) (3361 3600) 1053 1066 Fax: (+55) 41 3361 3141 e-mail: paulojus AT ufpr br http://www.leg.ufpr.br/~paulojus On Wed, 29 Apr 2015, Carlo Innocenti wrote: Thank you Edzer.
It works, but I need the back transformation as well. What about the gaussian anamorphosis with hermite polynomials? I know that is a method used to normalize the data before to apply the conditional gaussian simulation. There is a package in R to transform and back transform with this method? Another method that is used in these cases should be the normal scores transformation: is it implemented in some package? Carlo 2015-04-28 22:32 GMT+02:00 Edzer Pebesma <edzer.pebesma at uni-muenster.de>: one way is the rank transform:
x = rgamma(100, 0.1) hist(x) y = qnorm((order(x)/(length(x) + 0.5))) qqnorm(y) but transforming your conditionally simulated values back will be tricky. And I'm not sure about the 0.5. On 04/28/2015 06:09 PM, Carlo Innocenti wrote:
I would like to perform a gaussian conditional simulation on a variable that is highly skewed. Could someone suggest me how to transform my variable in a gaussian distribution? Thanks, Carlo
-- Edzer Pebesma Institute for Geoinformatics (ifgi), University of M?nster, Heisenbergstra?e 2, 48149 M?nster, Germany; +49 251 83 33081 Journal of Statistical Software: http://www.jstatsoft.org/ Computers & Geosciences: http://elsevier.com/locate/cageo/ Spatial Statistics Society http://www.spatialstatistics.info
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Carlo Innocenti, PhD
ISPRA
Istituto Superiore per la Protezione e la Ricerca Ambientale
High Institute for Environmental Protection and Research
Via Vitaliano Brancati, 60
00144 Roma
Italy
phone: +39 06 5007 4639
email: carlo.innocenti at isprambiente.it
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Carlo Innocenti, PhD ISPRA Istituto Superiore per la Protezione e la Ricerca Ambientale High Institute for Environmental Protection and Research Via Vitaliano Brancati, 60 00144 Roma Italy phone: +39 06 5007 4639 email: carlo.innocenti at isprambiente.it [[alternative HTML version deleted]]