[R] Managing output

[Oliver Bandel]

Noah Silverman <noah <at> smartmediacorp.com> writes:

> 
> Hi,
> 
> Is there a way to build up a vector, item by item.  In perl, we can 
> "push" an item onto an array.  How can we can do this in R?
> I have a loop that generates values as it goes.  I want to end up with a 
> vector of all the loop results.
> 
> In perl it woud be:
> 
> for(item in list){
>      result <- 2*item^2 (Or whatever formula, this is just a pseudo example)
>      Push(@result_list, result)  (This is the step I can't do in R)
> }
> 

Just do add an item at the end.

Example:


> mydat <- 1
> mydat[2] <- 33
> mydat[3] <- -4
> mydat[4] <- 12
> mydat[length(mydat)+1] <- 22
> mydat
[1]  1 33 -4 12 22
> mydat[length(mydat)+1] <- 5623
> mydat
[1]    1   33   -4   12   22 5623
> mydat[length(mydat)+1] <- 0.8962
> mydat
[1]    1.0000   33.0000   -4.0000   12.0000   22.0000 5623.0000    0.8962

When doing it in a loop, don't use length() over and over,
just count up the index.

For many entries, it would be faster, if you just allocate
the array that should be written, by just writing 0 into it,
or empty strings or something like this...
> mydat[1:100] <- 0
> mydat
  [1] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 [38] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
 [75] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
> mydat <- 1
> mydat[2] <- 33
> mydat[3] <- -4
> mydat
[1]  1 33 -4


instead of "mydat[1:100] <- 0"
use the length of the itemlist as second parameter.

Ciao,
  Oliver