[R] Odp: How to select randomly from a matrix?

[Petr PIKAL]

Hi

r-help-bounces at r-project.org napsal dne 09.03.2009 11:29:41:

> 
> Dear all,
> 
> I got one problem here and hoping someone can help me on this. Say I 
have a
> 50 by 2 matrix and I don't know how to randomly select:
> 
> 1. a pair of observations from the last 10th of the 50 observation from 
the
> matrix.


Use ?tail for ?nrow of matrix and ?sample this and select appropriate row 
from matrix


> 2. how to select randomly an observation from the first 5 observations 
of
> the second column in the matrix?

the same principle applies here but use head instead.

Regards
Petr

> 
> Thanks....hope to hear from someone soon
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