## Friday, May 16, 2014

### Sample uniformly within a fixed radius.

I was asked how to do this today and thought that I would share the answer:
```## Sample points uniformly within a fixed radius

nrand=1000
maxstep=10

## Sample data
## NB: To get a truly uniform sample over the circle, you must
##     sample the square of the distance and then transform back.
tempdat<-data.frame(X0=0,Y0=0, bearing0=0,
dist2=sqrt(runif(nrand)*maxstep^2),
turningangle=runif(nrand)*2*pi-pi)

##convert Turning angle to bearing (in this case no change)
tempdat\$bearing=tempdat\$bearing0+tempdat\$turningangle

## Convert from polar to cartesian coordinates
tempdat\$X<-tempdat\$X0+tempdat\$dist2*sin(tempdat\$bearing)
tempdat\$Y<-tempdat\$Y0+tempdat\$dist2*cos(tempdat\$bearing)

##make plots
png(filename="sampleplots.png",width=500,height=1000)
par(mfrow=c(2,1))
plot(Y~X, data=tempdat, asp=1, main="Uniform across space")
dev.off()
```

## Monday, April 28, 2014

### RStudio and X2Go

After a recent system upgrade (to Linux Mint LMDE), I was no longer able to run RStudio through the remote desktop application X2Go. It turns out that this is due to a problem with the Qt libraries (see this website). As suggested here, I just deleted all the Qt libraries used by RStudio:

`sudo rm  /usr/lib/rstudio/bin/libQt* `
` `

and all was well. (NB, the specific link to these files will vary depending on the flavor of Linux you use.)

**EDIT: If you are installing this on pure Debian (I just confirmed this with a new Jessie install) you will need to install appropriate libraries too:

`sudo aptitude install libqtwebkit4`
` `