[R] eval and assign in loop problem

[Erik Iverson]

> 
> for (i in 0:3)
>        {
>            r = runif(1)
>            assign(paste('b',i,sep=''),r)
>        }
> 
> 
> for (i in 1:4)
>        {
> 
> assign(paste('b',i,sep=''),eval(parse(text=paste('b',i-1,sep=''))))
>        }
> 

First, b1 is set to b0
Then,  b2 is set to b1 (which was just set to b0)
Then,  b3 is set to b2 (which was just set to b1, which was just set to b0)

...

All b[i] are set to b0

If this is all you're trying to accomplish, it's much better to keep the 
common objects in a vector (or list if they are more complicated) and 
use sapply/lapply and vectorized functions to perform the manipulations. 
You've managed to use three seldom-needed methods in 2 lines of R code 
:) (for loops, assign, and eval(parse(text=)))