[R-sig-Geo] Cryptic warning when reading raster which consists only of NULL

[Rainer M Krug]

Hi

When reading a raster from GRASS which consists only of NULL, a cryptic
warning is received:

,----
| Warning in lapply(lres, as.numeric) : NAs introduced by coercion
`----

This is caused by the line

,----
| lres <- lapply(lres, as.numeric)
`----

in the debug session below:

,----
| debug: con <- textConnection(tx)
| Browse[2]> 
| debug: res <- read.dcf(con)
| Browse[2]> 
| debug: close(con)
| Browse[2]> 
| debug: lres <- as.list(res)
| Browse[2]> 
| debug: names(lres) <- colnames(res)
| Browse[2]> 
| debug: lres <- lapply(lres, as.numeric)
| Browse[2]> 
| Warning in lapply(lres, as.numeric) : NAs introduced by coercion
| Warning in lapply(lres, as.numeric) : NAs introduced by coercion
| debug: if (!is.numeric(lres$min) || !is.finite(as.double(lres$min))) NODATA <- as.integer(999) else {
|     lres$min <- floor(as.double(lres$min))
|     NODATA <- floor(lres$min) - 1
| }
| Browse[2]> lres
| $min
| [1] NA
| 
| $max
| [1] NA
| 
| Browse[2]> tx
| [1] "min:NULL" "max:NULL"
| Browse[2]> 
`----

I would suggest to add thwe statements

,----
| if (lres[[1]]=="NULL") lrews[[1]] <- NA
| if (lres[[2]]=="NULL") lrews[[2]] <- NA
`----

before the line

,----
| lres <- lapply(lres, as.numeric)
`----

as this would replace the "NULL" with NA and not cause the error.

,----
| > sessionInfo()
| R version 3.0.1 (2013-05-16)
| Platform: x86_64-apple-darwin10.8.0 (64-bit)
| 
| locale:
| [1] C
| 
| attached base packages:
| [1] stats     graphics  grDevices utils     datasets  methods   base     
| 
| other attached packages:
|  [1] asmDrak_0.0-1        maptools_0.8-27      simecol_0.8-2       
|  [4] lattice_0.20-23      deSolve_1.10-7       prioritization_0.0-1
|  [7] seedGerm_0.0-1       seedDisp_0.4-13      Rcpp_0.10.4         
| [10] seedProd_0.0-1       fireSim_0.0-1        RSQLite_0.11.4      
| [13] DBI_0.2-7            spgrass6_0.8-3       XML_3.95-0.2        
| [16] sp_1.0-13            logger_0.0-1         devtools_1.3.99     
| 
| loaded via a namespace (and not attached):
|  [1] RCurl_1.95-4.1 compiler_3.0.1 digest_0.6.3   evaluate_0.4.7 foreign_0.8-53
|  [6] grid_3.0.1     httr_0.2       memoise_0.1    parallel_3.0.1 stringr_0.6.2 
| [11] tools_3.0.1    whisker_0.3-2 
| 
| > version
|                _                           
| platform       x86_64-apple-darwin10.8.0   
| arch           x86_64                      
| os             darwin10.8.0                
| system         x86_64, darwin10.8.0        
| status                                     
| major          3                           
| minor          0.1                         
| year           2013                        
| month          05                          
| day            16                          
| svn rev        62743                       
| language       R                           
| version.string R version 3.0.1 (2013-05-16)
| nickname       Good Sport      
`----

Thanks,

Rainer


-- 
Rainer M. Krug

email: RMKrug<at>gmail<dot>com
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