I'm using randomForest in yaImpute to create a yai-type object which 
associates "L" with landscape features. Then I use the sp() package to 
impute L to a landscape consisting of four ascii files) I keep getting the 
message "NA's generated due to illegal level(s)" when I do the imputation. 
It's probably because one of the landscape features ("as", for 
aspect/slope) is stored in numeric form but is treated as a factor when 
the yai object is created. "as" is also stored in numeric form in the 
ascii grids, of course. I included an "xtypes" argument in the 
AsciiGridImpute statement, but that did 
not help. Some relevant statements are:

xfiles <- list(DEM_10 = "dem_10.asc", EASTING = "easting.asc", 
        NORTHING = "northing.asc", as = "asp_slop.asc")

AsciiGridImpute(yai_ob, xfiles, outfiles,
        xtypes=list("numeric", "numeric", "integer", "character"))

Any insights will be appreciated. I'd particularly like to know how to 
gain access to the "invisible" list, VALUE, containing unexpectedNA's, 
illegal levels, and other information that would help me to troubleshoot 
the issue.

Dr. Seth  W. Bigelow
Biologist, USDA-FS Sierra Nevada Research Center
1731 Research Park Drive, Davis California
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