Blog Archives

Sample uniformly within a fixed radius.

May 16, 2014
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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 radiusnrand=1000maxstep=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, bad.dist= runif(nrand)*maxstep,...

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RStudio and X2Go

April 28, 2014
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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...

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Quantitative Ecology 2010-11-10 14:56:00

November 10, 2010
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At last... I have been suffering with XEmacs displaying odd characters instead of the quotation marks that are used in R help files. This was driving me up the wall because it makes the files (and R output in general) very hard to read; however, I fina...

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ISO week

October 22, 2009
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I am working with a model that produces estimates of snow water equivalent through time. Because I deal with large spatial extents, I decided to have the model produce weekly averages. The problem with this is knowing which file to access for a given d...

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Leap years

October 22, 2009
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A quick function that when provided a numeric vector of years returns a boolean vector where TRUE == Leap year.is.leapyear=function(year){ #http://en.wikipedia.org/wiki/Leap_year return(((year %% 4 == 0) & (year %% 100 != 0)) | (year %% 400 == 0))}

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Truncated Normal Distribution

September 3, 2009
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Many distributions may be used to describe patterns that are non-negative; however, there are not as many choices when an upper bound is also needed (although the beta distribution is very flexible). For various reasons, truncated distributions are som...

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R matrices in C functions

December 13, 2008
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Using the .C() function in R, you can only pass vectors. Since R stores matrices columnwise as vectors anyhow, they can be passed to your C function as vectors (along with the number of rows in the matrix) and then accessed in familiar manner...

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Call C from R and R from C

November 17, 2008
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Several years ago, while a research associate at the University of Chicago, I had the privilege of sitting in on a course taught by Peter Rossi: Bayesian Applications in Marketing and MicroEconometrics. This course -- one I recommend to anyone at U Chicago who is interested in statistics -- was an incredibly clear treatment of Bayesian...

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Error capture

May 6, 2008
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In a recent post to r-sig-ecology, Mike Colvin suggested the following to capture errors within a loop:for (i in 1:1000){fit<-try(lm(y~x,dataset))results<- ifelse(class(fit)=="try-error", NA, fit$coefficients)}

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Plotting contours

March 18, 2008
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Plotting contours

Plenty of packages allow you to plot contours of a "z" value; however, I wanted to be able to plot a specific density contour of a sample from a bivariate distribution over a plot that was a function of the x and y parameters. The example only plots th...

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