[R] Using the R commands

[Peter Dalgaard BSA]

ripley at stats.ox.ac.uk writes:

> On Sat, 29 Mar 2003, Jonathan Baron wrote:
> 
> > On 03/30/03 03:25, Marcus V. Stecklow wrote:
> > 
> > >I`m doing a program and it`s have a loop using the for command. inside the 
> > >loop i have a variable and in each step of loop she have a new value.
> > >
> > >The question is: How can i store the values and make a table?
> > 
> > For example:
> > Squares <- rep(NA,10) # make an empty vector with 10 places
> > for (i in 1:10) Squares[i] <- i^2 # fill it with squares
> > Squares # print it
> > 
> > Lots of other ways to do this.  For example, you can use
> > Squares <- {}
> > for the first step.
> 
> The best idea is start out with a vector of the correct length and the 
> correct type (rep(NA, 10) is logical), e.g.
> 
> Squares <- numeric(10)
> 
> This helps for long vectors by reducing the number of copies made.
> Squares <- {} is equivalent to setting the result to NULL, just more
> obscure.

And also note that many of these cases are more succinctly expressed
using implicit loops, like

Squares <- sapply(1:10,function(x)x^2)

or even

Squares <- sapply(1:10,"^",y=2)


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
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