[R] Spliting a huge vector

Petr Pikal petr.pikal at precheza.cz
Thu Sep 21 09:42:21 CEST 2006


On 20 Sep 2006 at 14:19, Dave Evens wrote:

Date sent:      	Wed, 20 Sep 2006 14:19:04 -0700 (PDT)
From:           	Dave Evens <devens8765 at yahoo.com>
To:             	r-help at stat.math.ethz.ch
Subject:        	[R] Spliting a huge vector

> Dear R users,
> I have a huge vector that I would like to split into
> unequal slices. However, the only way I can do this is
> to create another huge vector to define the groups
> that are used to split the original vector, e.g.
> # my vector is this
> a.vector <- seq(2, by=5, length=100)

should not it be

a.vector <- seq(2, by=5, length=803)

> # indices where I would like to slice my vector
> cut.values <- c(30, 50, 100, 109, 300, 601, 803)
> # so I have to create another vector of similar length
> # to use the split() command, i.e.
> x <- rep(1:length(cut.values), times=diff(c(0,
> cut.values))

here it throws syntactic error so I assume it shall have one more 

> # this means I can use split()
> split(a.vector, x)
times <- diff(c(0,cut.values))

do.call(function(x, y, times) split(x,rep(y, times=times)), 
list(x=a.vector, y= cut.values, times=times))


split(a.vector,rep(1:length(cut.values), times=times))

is this what you want? However I am not sure that some vector is not 
created internally.


> This seems to be a waste in terms of memory usage as
> I'm creating another vector (here "x") to split the
> original vector. Is there a better way to split a huge
> vector than this? Any help is much appreciated. 
> Best,
> Dave.
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Petr Pikal
petr.pikal at precheza.cz

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