[R] Generation of random numbers in a function - (Return command)

[jim holtman]

You can only return a single object.  You might want to create a list
if you have multiple objects:

return(list(output_avg_mc, output_stdev_mc))


On Fri, Mar 11, 2011 at 10:51 AM, Vincy Pyne <vincy_pyne at yahoo.ca> wrote:
> Dear R helpers
>
> I have following data.frame and for each product_name, I have associated mean and standard deviation. I need to generate 1000 random no.s for each of these products and find the respective mean and standard deviation.
>
> My R code is as follows.
>
>
> library(plyr)
> library(reshape2)
>
> filtered_new <- data.frame(product_name = c("P1", "P2", "P3", "P4", "P5"),
> output_avg = c(22.71078,22.16979,21.34420,20.17421,19.83799),
> output_stdev = c(23.59924,21.21430,22.01025,18.88877,18.80436))
>
> n <- 100
>
> myfunction_mc = function(product_name, output_avg, output_stdev)
>
> {
>
> product_usage_borrowing_room_mc = rnorm(n, output_avg, output_stdev)
>
> output_avg_mc =
>  mean(product_usage_borrowing_room_mc)
> output_stdev_mc = sd(product_usage_borrowing_room_mc)
>
> return(output_avg_mc )
>
> }
>
> result <- dlply(.data = filtered_new, .variables = "product_name", .fun = function(x)
>                  myfunction_mc(product_name = x$product_name, output_avg = x$output_avg,
>                  output_stdev = x$output_stdev))
>
> result1 <- data.frame(result)
>
> result2 <- melt(result1)
>
> result <- data.frame(product = filtered_new$product_name, Monte_Carlo_result = result2$value)
>
> And it gives me the desired result.
>
>
> ######### PROBLEM is as given below -
>
> But if in the "myfunction_mc", in the return statement if I try to add 'output_stdev_mc'
>  i.e.
>
> myfunction_mc = function(product_name, output_avg, output_stdev)
>
> {
>
> product_usage_borrowing_room_mc = rnorm(n, output_avg, output_stdev)
>
> output_avg_mc = mean(product_usage_borrowing_room_mc)
> output_stdev_mc = sd(product_usage_borrowing_room_mc)
>
> return(output_avg_mc, output_stdev_mc)            # I have added output_stdev_m
>
> }
>
> result <- dlply(.data = filtered_new, .variables = "product_name", .fun = function(x)
>                  myfunction_mc(product_name = x$product_name, output_avg = x$output_avg,
>                  output_stdev = x$output_stdev))
>
> I get following error -
>
> Error in return(output_avg_mc, output_stdev_mc) : multi-argument returns are not permitted
>
> Kindly
>  guide.
>
> Regards
>
>
> Vincy
>
>
>        [[alternative HTML version deleted]]
>
>
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>
>



-- 
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?