[R] Probably a good use for apply

[Sarah Goslee]

Hi,

On Thu, May 31, 2012 at 1:08 PM, LCOG1 <jroll at lcog.org> wrote:
> This is great thank you.  I think I am getting the hang of some of the apply
> functions.  I am stuck again however.  I have list test_ below and would
> like to apply the sample function using each element of each vector as the
> probability and return a TRUE or FALSE that I will ultimately sum the TRUES
> by vector.
>
> test_<- list(a=c(.85,.10),b=c(.99,.05))
> #Write a function to sample based on labor force participation rates to
> determine presence of workers in household
> sampleWorker <- function(x) return(sample(c(TRUE,FALSE),x, replace = TRUE,
> prob = c(x, 1-x)))

Your first problem is that sampleWorker() doesn't run with a single
component of test_ so it can't possibly run in an apply statement.

Please reread ?sample - the second argument is the size of the desired
sample, but what you are passing is a non-integer vector of length 2.
What do you actually want this to be?

Then for prob, you're passing c(x, 1-x)) but x is again a non-integer
vector of length 2, so that results in a vector of length 4, which is
longer than the number of options sample() is choosing from.

Do you perhaps want to pass only a single probability at a time? But
even then you need to resolve the size problem.

Sarah

> IsWorker.Hh_ <- lapply(test , sampleWorker)
>
> I am doing something wrong with the setup becuase i am getting an error
> about specifying probabilities incorrectly.
>
> The result I am looking for for  IsWorker_ to be (assuming the .85, and . 99
> probabilities 'win' from each vector and the lower values do not.
>
>> IsWorker_
> $a
> [1]TRUE
> $b
> [1]TRUE
>
> but ultimately I will need to sum the TRUEs for each vector
>
>> IsWorker_
> $a
> [1] 1
> $b
> [1] 1
>
>
> Thanks
>
> Josh
>

-- 
Sarah Goslee
http://www.functionaldiversity.org