Stochastic Nonsense

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

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 port install postgresql84

in a shell, create an environmental variable PG_CONFIG pointing to the pg_config binary installed [...]

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Querying Databases From R on a Mac

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 on the mac is a 64 bit app. So, I want to use [...]

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Querying Postgres or Greenplum from R on a Mac

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 app that you have to download from apple here . Now all [...]

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Querying Databases in R

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 have RODBC installed, you call it in R as follows. But it’s very simple: a bit [...]

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R Dates – Recovering and Converting From Integers

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 in the first line, we take the range of dates present in our data, [...]

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Examining Data Frames — head and tail

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:

> d d
> str(d)
‘data.frame’: 50 obs. of 2 variables:
$ mean: int 1 [...]

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Removing Extra Column of Data from CSVs in R — R Tip

When R writes a csv file, you get an extra column of data as such:

> s
> plot(x=s$x, y=s$y )
>
> write.csv(x=s, file=’s0.csv’ )

When you peek in the csv file, you see this:

blog earl$ head s0.csv
“”,”x”,”y”
“1″,1,8.29164186026901
“2″,2,2.83956938423216
“3″,3,7.43510165950283
“4″,4,6.38210728997365
“5″,5,9.29241271456704
“6″,6,6.13102467032149
“7″,7,5.03747826907784
“8″,8,1.83257902506739
“9″,9,9.62789378128946
blog earl$

What is that first column? It’s actually pretty obvious in this example, but if you’ve sorted your data frame [...]

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Examining CSV Data Columns From a Shell

It’s very handy to be able to pop open a shell and peek in your csv files. awk is a command that will do just that — it divides each line into fields based either on a whitespace separator or by a separator specified by -F. Here’s a script that prints the 8th [...]