April 2008

speed issue in R computing: apply() vs a loop

April 23, 2008 | Yu-Sung Su

In R, apply() is NOT faster than a loop!!I don't know where I pick up this perception about apply() being faster than a loop in R. For a long time, I always think that apply() runs a function (for example, mean()) on a data structure (row or column) i... [Read more...]

An R Wiki

April 21, 2008 | nsaunders

It’s been ages since I visited the R website, so I don’t know how long they’ve had a wiki. It’s built using DokuWiki, one of my personal favourites. This is a great leap forward for R documentation, which is somewhat notorious for being (a) difficult to ... [Read more...]

Heteroscedasticity

April 6, 2008 | vikasrawal

If a model is estimated using the following code: lm(y~x1+x2)-__p 1. bptest(p) does the Breuch Pagan test to formally check presence of heteroscedasticity. To use bptest, you will have to call lmtest library. 2. If the test is positive (low p value), you should see if ... [Read more...]

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