[R] ‘ips’ had non-zero exit status

[giovanni_gmail]

dear all,
sorry for the naive question,
I'm trying to install (in R version 3.2.1 (2015-06-18))  the "ips" 
package for phylogenetic analysis.
However I get the following message:


 > install.packages("ips",dependencies = T)
Installing package into ‘/home/giovanni/R/x86_64-pc-linux-gnu-library/3.2’
(as ‘lib’ is unspecified)
also installing the dependency ‘XML’

provo con l'URL 'https://cran.rstudio.com/src/contrib/XML_3.98-1.3.tar.gz'
Content type 'application/x-gzip' length 1607725 bytes (1.5 MB)
==================================================
downloaded 1.5 MB

provo con l'URL 'https://cran.rstudio.com/src/contrib/ips_0.0-7.tar.gz'
Content type 'application/x-gzip' length 62904 bytes (61 KB)
==================================================
downloaded 61 KB

* installing *source* package ‘XML’ ...
** package ‘XML’ successfully unpacked and MD5 sums checked
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking how to run the C preprocessor... gcc -E
checking for sed... /bin/sed
checking for pkg-config... /usr/bin/pkg-config
checking for xml2-config... no
Cannot find xml2-config
ERROR: configuration failed for package ‘XML’
* removing ‘/home/giovanni/R/x86_64-pc-linux-gnu-library/3.2/XML’
Warning in install.packages :
   installation of package ‘XML’ had non-zero exit status
ERROR: dependency ‘XML’ is not available for package ‘ips’
* removing ‘/home/giovanni/R/x86_64-pc-linux-gnu-library/3.2/ips’
Warning in install.packages :
   installation of package ‘ips’ had non-zero exit status

The downloaded source packages are in
     ‘/tmp/RtmpbTmMtc/downloaded_packages’

can anybody help me?
best regards
Giovanni