## Meet the cloud that will keep you warm at night

You already have a physical presence at your customers, why not give them a distributed data center too? German company AoTerra is building OpenStack into their heating systems.

Will the lower hardware and HVAC requirements out weight operating costs born of density in a traditional data center? I can’t wait to find out.

## OpenShift.com – Now With R and rpy2

A couple of weeks ago, I announced successfully installing and running R/rpy2 on OpenShift.com

Now, you can grab the installation process and bits for yourself* through github.

http://github.com/emorisse/ROpenShift

*I’d prefer (and will be thankful for) commits, hacks, advice, and ideas over code branches.

## Calculating Conditional Entropy in R

```conditionalEntropy <- function( graph ) {
# graph is a 2 or 3 column dataframe
if (ncol(graph) == 2 ) {
names(graph) <- c("from","to")
graph\$weight <- 1
} else if (ncol(graph) == 3)
names(graph) <- c("from","to","weight")
max <- length(rle(paste(graph\$from, graph\$to))\$values)
total <- sum(graph\$weight)
entropy <- data.frame(H = 0, Hmax = 0);
entropy\$H <- sum(graph\$weight/total * log(graph\$weight/total) / log(2)) * -1
entropy\$Hmax <- log(max * (max-1))/log(2)
return(entropy)
}```