Question

How to find out the package version which is loaded in R

Answer 1

You can use sessionInfo() to accomplish that.

> sessionInfo()
R version 2.15.0 (2012-03-30)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C               LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8    LC_PAPER=C                 LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C             LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

attached base packages:
[1] graphics  grDevices utils     datasets  stats     grid      methods   base     

other attached packages:
[1] ggplot2_0.9.0  reshape2_1.2.1 plyr_1.7.1    

loaded via a namespace (and not attached):
 [1] colorspace_1.1-1   dichromat_1.2-4    digest_0.5.2       MASS_7.3-18        memoise_0.1        munsell_0.3       
 [7] proto_0.3-9.2      RColorBrewer_1.0-5 scales_0.2.0       stringr_0.6       
>
However, as per comments and the answer below, there are better options

> packageVersion("snow")
[1] ‘0.3.9’

Or:

"Rmpi" %in% loadedNamespaces()