[R] storing the results of an apply call

[David Winsemius]

On Aug 11, 2010, at 7:51 PM, Lorenzo Cattarino wrote:

> Hi R-users,
> I have a function (myfun) that I want to apply to the rows of a  
> matrix.
> Basically, "myfun" takes the values from the matrix ("exp.des"), which
> represent the different combinations of my experimental design, and  
> pass
> them as arguments to some other functions (fun1 and fun2). As I want  
> to
> replicate the results of fun1 and fun2 a certain number of time (e.g.
> 5), I have a for loop within myfun.
>
> I would like to store the results of each iteration of fun1 and fun2  
> in
> a separate matrix ("output") but I have some problems telling R  
> which is
> the position of "output" where to store the results. It seems that  
> every
> time "myfun" is applied to each row of "exp.des", the position  
> restarts
> from 1, without being updated (like I am trying to make it doing).  
> Here
> is an example of what I am talking about:
>
> output <- matrix (, 15, 1)
>
> index <- 1
> myfun <- function(x)
> {
>   bla  # goes against the Posting Guide directive to produce  
> reproducible code
>   bla #  ...  if it doesn't matter than leave it out or use "#"
>   bla
>   ...
>   for (i in 1:Rep)  #  Rep not defined
> # the blank lines are also a barrier to comprehension
>  {
>     res1 <- fun1(....) # more useless junk
>    res2 <- fun2(res1,....)
>    output [index,1]<- res2$something
>    index <- index+1
>   }
>   return(output) # so you will get one of "output" per line of  
> matrix or dataframe

# But /// ...  it does not (or at least should not in my understanding  
of scoping) go into in that "output" object that you defined outside  
the "myfun" function.
> }
> apply(exp.des, 1, myfun)

Would do absolutely nothing since you did not assign the output of the  
"output's  from apply() to any object. Lexical scoping. If you do not  
understand the term then do some more reading.
>
>
> Learn to post in plain text please. This is a plain text mailing  
> list. Ix-nay on the T-M-L-Hay.
>      [,1] [,2] [,3]
>
> [1,]   23    5   99
>
> [2,]    6   45   18
>
> [3,]    1   65    9
>
> [4,]    9   10   45
>
> [5,]    3   30    9
>
> [6,]   NA   NA   NA
>
> [7,]   NA   NA   NA
>
> [8,]   NA   NA   NA
>
> [9,]   NA   NA   NA
>
> [10,]   NA   NA   NA
>
> [11,]   NA   NA   NA
>
> [12,]   NA   NA   NA
>
> [13,]   NA   NA   NA
>
> [14,]   NA   NA   NA
>
> [15,]   NA   NA   NA
>
>
> I would like to have just one column with the three groups of five
> values.
>
> Many thanks
> Lorenzo
> \

David Winsemius, MD
West Hartford, CT