Posts Tagged ‘ Research ’

Converting vectors to numeric in mixed-type dataframe

May 19, 2011
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Coercing variables of character and numeric type into a single dataframe yields all vectors to be defined as factors all <- data.frame(cbind(site, year, model, x, y, z)) The following converts selected variables from “factor” back to “numeric” all$x <- as.numeric(x) … Continue reading →

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How to do a quantitative literature review in R

May 17, 2011
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How to do a quantitative literature review in R

In the early stages of a literature review, you may have hundreds of papers and not know how to even begin sorting through them. In this post, I show you how to perform a two-stage clustering analysis with R so that you can identify the main groups within your data, based on key attributes of each paper.

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Mapping points

May 16, 2011
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Mapping points

Since I look at mercury concentrations at different measurement stations in North America, visualization using a map with values (of your favourite parameter) plotted as colour-coded circles is quite useful. After some trial & error, here is some very basic code … Continue reading →

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Is R an ideal language to teach the fundamentals of programming to beginners?

May 6, 2011
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Is R an ideal language to teach the fundamentals of programming to beginners?

I’m helping out some colleagues learn programming from having zero experience with it in any shape or form. It’s quite a daunting task in some senses, because, well, it may not be easy! They are researchers, so they’ll need it for processing data and generating output, and perhaps processing BIG DATA at some point too.

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Unable to plot a decent x-Axis in a time series plot using zoo

April 7, 2011
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I use the R package zoo to plot a yearly time series of weekly averaged data. The problem is that my date variable (m.all$date) contains week numbers and these are plotted as x-Axis. What I would rather like to to … Continue reading →

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More fun with sed

March 18, 2011
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So I have this strange date and time string, which I would like to convert to a “useable” date, i.e., something that a spreadsheet programme or R can work with. It looks like this (MON has 3 chars): ddMONyr:hh:mm:ss The … Continue reading →

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Converting text files with sed

March 3, 2011
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Sed is my friend to change fixed-width text files (e.g., from an R screen output) to a comma delimited file using sed 's/ */,/g' file1 >file2.csv Note the two spaces between s/ and */.

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Model for nothing – and the bootstrap for free

January 21, 2011
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Model for nothing – and the bootstrap for free

Reconstructing phylogenies is an interesting task, sadly one that often requires to navigate between a multitude of software. To add an unnecessary layer of complexity to the whole thing, most of these softwares speaks different languages, and requires the user to do endless conversions from fasta to phylip to nexus to whatever new format they

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A (fast!) null model of bipartite networks

September 12, 2010
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A (fast!) null model of bipartite networks

One of the challenges for ecologists working with trophic/interaction networks is to understand their organization. One of the possible approaches is to compare them across a random model, with more or less constraints, in order to estimate the departure from randomness. To this effect, null models have been developed. The basic idea behind a null

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A small and lonely sea urchin…

August 22, 2010
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A small and lonely sea urchin…

A few weeks ago, a paper on which I am a co-author was accepted for publication in the french ecological journal Life & Environment. In this paper, we evaluate the consequences of recreative harvesting on three populations of sea urchins (…)Read the rest of this entry »

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