[R] faster vector subtraction??

[Prof Brian Ripley]

On Wed, 16 Jan 2002, [iso-8859-1] Søren Merser wrote:

> hi
> is there a faster way to do this?
>
> i <- 1
> for(x in vector1)
>      for(y in vector2) {
>          m[[i]] <- (x - y)
>          i <- i + 1
>       }

outer and as.list (but why do you want a list)?

outer(vector1, vector2, "-") is a good start, and
as.list(-outer(vector2, vector1, "-"))
seems to reproduce your loops.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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