R crashes if "toFile" given "~/" in Linux envirnonment

I was running some sample code from a help page tonight and wished to
redirect the sample output to my Desktop under Linux (Mint-Debian 64 if it
makes a different). I was surprised to find that file name expansion using
the ubuquitious "~/" was not recognized, in fact it caused R to crash. Is
this expected behavior? See my output below and sessionInfo().  Also, not
shown, but 'setwd("~/Desktop")' works just fine.  Thanks, Mark

# sample code from Rgraphviz clusterData help page
library(graph)
library(Rgraphviz)
g1_gz <- gzfile(system.file("GXL/graphExample-01.gxl.gz",package="graph"),
open="rb")
g11_gz <- gzfile(system.file("GXL/graphExample-11.gxl.gz",package="graph"),
open="rb")
g1 <- fromGXL(g1_gz)
g11 <- fromGXL(g11_gz)
g1_11 <- join(g1, g11)
sgl <- vector(mode="list", length=2)
sgl[[1]] <- list(graph=g1, cluster=TRUE)
sgl[[2]] <- list(graph=g11, cluster=TRUE)
ng <- agopenSimple(g1_11, "tmpsg", subGList=sgl)
clusterData(ng, 1, c("bgcolor")) <- c("blue")
clusterData(ng, 2, c("bgcolor")) <- c("red")
############################################
# and now 2 usually equivalent ways to specify the location for output file,
with the second way crashing:
toFile(ng, layoutType="dot", filename="/home/mkimpel/Desktop/g1_11_dot.ps",
fileType="ps")
NULL
toFile(ng, layoutType="dot", filename="~/Desktop/g1_11_dot.ps",
fileType="ps")
~/Desktop/g1_11_dot.ps: No such file or directory

Process R exited abnormally with code 1 at Mon May 16 22:42:12 2011
#################################################
# and my sessionInfo()
R version 2.13.0 (2011-04-13)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
[1] LC_CTYPE=en_US.utf8       LC_NUMERIC=C
LC_TIME=en_US.utf8        LC_COLLATE=en_US.utf8     LC_MONETARY=C

[6] LC_MESSAGES=en_US.utf8    LC_PAPER=en_US.utf8
LC_NAME=C                 LC_ADDRESS=C              LC_TELEPHONE=C

[11] LC_MEASUREMENT=en_US.utf8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base
####################################################
Mark W. Kimpel MD  ** Neuroinformatics ** Dept. of Psychiatry
Indiana University School of Medicine

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