[R-sig-Geo] Can't run mk.test for raster stack

[Mandakh Nyamtseren 2]

Dear all,I'm trying to use MannKendall test to get trend of 10 year aridity data. Can some one help me to correct this code. 
>library(raster)
>library(trend)
>setwd("D:/ClimateData/MK_aridity")
>list <- list.files(pattern = "*.asc")
>RasterStack <- Stack(list)
>test <- calc(r, fun=function(x) {return(unlist(mk.test(x)))}, na.rm)
When I run I receive messege : 
Error in .calcTest(x[1:5], fun, na.rm, forcefun, forceapply) : 
  cannot use this function
In addition: Warning messages:
1: In .HTMLsearch(query) : Unrecognized search field: title
2: In .HTMLsearch(query) : Unrecognized search field: keyword
3: In .HTMLsearch(query) : Unrecognized search field: alias


The raster has a portion of pixels with NA values. 
Thank you in advance for your help. 

Sincerely, 

Ms. N.Mandakh
Division for Desertification Study
Institute of Geography and Geoecology Mongolian Academy of Sciences

Baruun Selbe-15
Ulaanbatar - 15170
Mongolia

Fax: 976-11-321862
Cellular: 976-99148380
E-mail: maaggi at yahoo.com, n.mandakh at gmail.com
	[[alternative HTML version deleted]]