[R] storing the results of an apply call

[Joshua Wiley]

On Wed, Aug 11, 2010 at 4:51 PM, Lorenzo Cattarino
<l.cattarino at uq.edu.au> 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

Yes, this is quite expected.  You define index outside of your
function and for loop, and proceed to only update it in your for loop
which is in your function.

> from 1, without being updated (like I am trying to make it doing). Here
> is an example of what I am talking about:

What follows is not really an example.  There is no real data, which
while annoying could be overcome, but we also do not have your
function.  Last I heard, present or future Greg (I mix them up) is
working on a ESP package, but I am pretty certain it has not been
released yet.

If it is not too terribly important that the results of apply() be in
the matrix as you want, why not simply reformat the data you have?

mymatrix <- matrix(c(1:15, rep(NA, 30)), ncol = 3, byrow = TRUE)
mymatrix
#Grab the first 5 rows of data and reformat them
matrix(mymatrix[1:5, ], ncol = 1)

Since apply() will combine all of its results anyways, I would get rid
of index and just have an internal index in the for loop.

Cheers,

Josh

>
>
>
> output <- matrix (, 15, 1)
>
> index <- 1
>
>
>
> myfun <- function(x)
>
> {
>
>  bla
>
>  bla
>
>  bla
>
>  ...
>
>  for (i in 1:Rep)
>
>  {
>
>    res1 <- fun1(....)
>
>    res2 <- fun2(res1,....)
>
>    output [index,1]<- res2$something
>
>    index <- index+1
>
>  }
>
>  return(output)
>
> }
>
>
>
> apply(exp.des, 1, myfun)
>
>
>
>      [,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
>
>
>
> Lorenzo Cattarino
>
> PhD Candidate (Confirmed)
>
>
>
> Landscape Ecology and Conservation Group
>
> Centre for Spatial Environmental Research
>
> School of Geography, Planning and Environmental Management
>
> The University of Queensland
>
> Brisbane, Queensland, 4072, Australia
>
> Telephone 61-7-3365 4370, Mobile 0410884610
>
> Email l.cattarino at uq.edu.au
>
> Internet http://www.gpem.uq.edu.au/cser <http://www.gpem.uq.edu.au/cser>
>
>
>
>
>
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>
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>



-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/