[R] R help on loops

[Berend Hasselman]

On 07-06-2013, at 11:57, Laz <lmramba at ufl.edu> wrote:

> Dear Berend,
> 
> I have made some changes but I still get errors:
> 
> For reproducibility, 
> Rspatswap() is a function which originally returns a single value. For example Rspatswap(...)  and you get 0.8 
> 
> So, run Rspatswap() 20 times and store all the values. 
> Then from these 20 values, calculate the calculate average, sd,se,min,max to get something similar to: 
> 
>         average           sd           se       min      max 
> trace 0.8880286 0.0009178193 0.0004589096 0.8870152 0.889241 
> 
> If we repeat the function 10 times, then I expect 10 rows with 5 columns but it does not work ? 
> 

Replacing Rspatswap(…)[1] with runif(1) (you could/should have done that to provide reproducible code) and the modifications I suggested you make in your function itn() like this

itn<-function(it){
siml<-matrix(NA,ncol=5,nrow=it)
  for(g in 1:it){
   siml[g,]<-optm(perm=20)
  }
siml
}

running itn(10) I get a matrix with 10 rows and 5 columns.

So what do you mean by "it does not work"?
You sometimes get an error message from apply due to a bad dim() like this

Error in apply(mat, 2, mean) : dim(X) must have a positive length

When the result of mat[-delete,] is a matrix with a single row the result is simplified to a vector. See ?"[" in particular the drop argument.
So this should work in function optm()

    mat <- mat[-delete,, drop=FALSE] 

Berend