Category Archives: R Tip

Unique is broken in R

Posted on July 9, 2011 by earl

Are you kidding me? $ R > unique(1,1,2,3,4) [1] 1 This was the source of yesterday’s nasty to track down bug. What you really want is unique on a vector, as in: > unique(c(1,1,2,3,4)) [1] 1 2 3 4 I … Continue reading →

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Finding the sort order of an array in R or Ruby

Posted on June 26, 2011 by earl

Suppose you have an array that you’d like to sort by another array. A common use case might be a set of arrays of somethings and for each something you generate a score in say [0,1]. Now you’d like to … Continue reading →

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Getting the value of a variable from a string in R

Posted on June 25, 2011 by earl

It’s often convenient to use reflection to get the value of a variable from the name as a string. In R, you can use the get function to do this. In R : blog $ R > x = 3 … Continue reading →

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Interactive Plotting in R

Posted on January 25, 2010 by earl

There are many ways to compare univariate distributions; one of my favorites is violin plots. However, if you are only comparing two distributions, then the best solution is often a scatter plot. To that end, I’ve build some code that … Continue reading →

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Querying Postgres or Greenplum From R on a Mac, Installation Instructions

Posted on January 21, 2010 by earl

NB: this works on 64b versions of R; I tested it with the R64 app with R version 2.10.1 on Snow Leopard Step by step instructions for talking to Postgres or Greenplum: install macports install postgres; I used 8.4 sudo … Continue reading →

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Querying Databases From R on a Mac

Posted on January 11, 2010 by earl

I use a mac, currently running OS 10.6 / Snow Leopard, and I’d like to query our greenplum / postgres database from R. This used to work with R 2.9, but I unfortunately had to upgrade R, and R 2.10 … Continue reading →

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Querying Postgres or Greenplum from R on a Mac

Posted on December 31, 2009 by earl

So, I’m using snow leopard, and I want to query our postgres / greenplum database. First things first: I’m familiar with the RODBC package on CRAN. This installs fine, since it’s a binary package. I also installed the ODBC Administrator … Continue reading →

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Querying Databases in R

Posted on August 14, 2009 by earl

One of the first things you’ll want to do in R is set it up to talk to databases. The easiest way to do this is using ODBC, via package RODBC. To get the package, run > install.packages(RODBC) Once you … Continue reading →

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R Dates – Recovering and Converting From Integers

Posted on August 12, 2009 by earl

One problem with R is that dates (class Date) are internally stored as integer numbers of days elapsed since 1 January 1970 and R sometimes loses the dateness of the variables and thinks of it only as an integer. So … Continue reading →

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Examining Data Frames — head and tail

Posted on August 2, 2009 by earl

head and tail, for those familiar with the unix command line, are two very handy utilities for looking at data frames. Along with str, which displays the structure of a data frame, they help you look at your data: > … Continue reading →

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