Dear Murray,
Here is one way:  create a function that takes k sample()s from any vector
(e.g., x) and then calculates the number of NA values in it. Then replicate
the procedure as many times as you want.

# The function
 foo <- function(x, k = 5){
                   xsample <- sample(x, k)
                   sum( is.na(xsample) )
                   }

# Vector of data
y <- c(1:10, NA, NA)

# The replication (10 replicates are used)
#  replicate(10, foo(y) )
#  [1] 1 2 1 1 0 0 1 0 1 1

HTH,

Jorge


On Wed, Jul 1, 2009 at 10:15 PM, Murray Cooper <myrmail@earthlink.net>wrote:

> Dear All,
>
> I am new to R and slowly learning how to use the system.
>
> The following code is an exercise I was trying.
> The intent is to generate 10 random samples of size 5 from
> a vector with integers 1:10 and 2 missing values. I then want
> to generate a matrix, for each sample which shows the frequency
> of missing values (NA) in each sample. My solution, using sapply
> is at the end.
>
> If anyone has the time and/or intrest to critique my method I'd
> be very grateful. I'm especially interested in knowing if there is
> a better way to accomplish this problem.
>
>  (x<-replicate(10,sample(c(1:10,rep(NA,2)),5)))
>>
>    [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
> [1,]    3   NA    3    4    2   10   NA    4    5     4
> [2,]    5    7    7    3    9    2    8   NA    7     9
> [3,]   NA    8    1    5   NA    7   10    2   NA     6
> [4,]    2   NA    6   10    8    4    4    7    4     7
> [5,]    7    9   10    8    3    6    1   NA    9    NA
>
>> # Since table will return only a single item of vaule FALSE
>> # if there are no missing values (NA) in a sample, sapply
>> # will return a list and not a matrix.
>> # So to get a matrix, the factor function needs to be used
>> # to identify possible results (FALSE, TRUE) for the table
>> # function.
>> sapply(1:10,function(i) table(factor(is.na(x[,i]),c(FALSE,TRUE))))
>>
>     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
> FALSE    4    3    5    5    4    5    4    3    4     4
> TRUE     1    2    0    0    1    0    1    2    1     1
>
>>
>>
> Thanks for your thoughts.
>
> Murray M Cooper, Ph.D.
> Richland Statistics
> 9800 N 24th St
> Richland, MI, USA 49083
> Mail: richstat@earthlink.net
>
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

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