[R] Equivalent of Mathematica's Apply

Franz Mueter fmueter at alaska.net
Tue Jun 24 22:30:01 CEST 2008


> apply(ind, 1, function(i) x[i[1]:i[2]])

which returns a matrix if all sequences are the same length, a list

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Juan Pablo Romero Méndez
Sent: Tuesday, June 24, 2008 11:51 AM
To: r-help at stat.math.ethz.ch
Subject: [R] Equivalent of Mathematica's Apply


Is there some equivalent function in R of Mathematica's "Apply"


Apply[ f, g[a,b]] ==> f[a,b]

In concret, I have a matrix of indexes:

> ind = cbind(1:5, 1:5+5)

> ind

     [,1] [,2]
[1,]    1    6
[2,]    2    7
[3,]    3    8
[4,]    4    9
[5,]    5   10

and I'd like to extract sequences 1:6, 2:7, 3:8, ..., 5:10  from a vector x.

What would be the most compact way of achieving this?

I've tried

 sapply(1:5, function(i) x[ind[i,1] : ind[i,2]])


 sapply(1:5, function(i) x[seq(ind[i,])])

would be better (if it worked).


  Juan Pablo

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