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

I am in a process of figuring out how to use my university cluster. It has 2 versions of R installed. System wide R 2.11 (Debian 6.0) and R 2.14.2 in non-standard location.

I am trying to use MPI together with snow. The code I am trying to run is the following

library(snow)
library(Rmpi)
cl <- makeMPIcluster(mpi.universe.size()-1)
stopCluster(cl)

mpi.quit()

It works without the problems on R 2.11. (I launch the script with mpirun -H localhost,n1,n2,n3,n4 -n 1 R --slave -f code.R). Now when I try to do it with R 2.14.2, I get the following message:

Error: This is R 2.11.1, package 'snow' needs >= 2.12.1
In addition: Warning message:

So it seems that R loads the package snow version compiled for R 2.11. I've installed snow under R 2.14 into my home folder and I added the following lines to my code:

.libPaths("/soft/R/lib/R/library")
.libPaths("~/R/x86_64-pc-linux-gnu-library/2.11")
print(.libPaths())
print(sessionInfo())
print(version)

And the output before the error confirms that I am indeed running R 2.14.2 and my R packages folder is first in search path. But I still get the error.

So my question is how do I determine which version of package is loaded in R? I can see with installed.packages all the packages which are installed, so maybe there is some function which lists similar information for loaded packages?

Answer

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()