[R] Problem looping a function to create/add to new dataframe

[David Winsemius]

On Sep 15, 2011, at 1:50 PM, Mike Treglia wrote:

> Dear List Members,
>
> I have created a function to run a simulation based on a given set  
> of values within a vector, such that I run the function like this:
>
> new.data<-sapply(vector, function)
>
> In which I run 'function' on every value within a vector that I  
> created. The result is a matrix of 1000 rows, and as many columns as  
> the length of the vector.
>
> I modified the function to utilize two given values, such that it  
> is: function(x,y), and I want to run this function for not only a  
> range of values of 'x', but a range of values of 'y' as well, such  
> that for each value of 'y', I'd create another 1000 rows in the  
> matrix. I was trying to loop this, but in doing so, it looks like I  
> just keep creating datasets and replacing them with datasets for  
> subsequent 'y' values, rather than adding new rows. The structure of  
> my current loop is below. Any suggestions on what to change to  
> accomplish what I want? Would it be good to create a dataframe first  
> and then somehow add these new rows to the dataframe? Also, is it  
> appropriate to have the 'i' in the sapply statement?

>
> for (i in c(seq(10,100,10))){

The c() call is extraneous.

>        new.data<-sapply(vector, function, i)



Perhaps:

# scrap the entire for loop(sapply()) mess and use this

newdata <- outer(Y=seq(10,100,10), X=vector, FUN=function)

Or:

mapply(function,  expand.grid(x=vector, y=seq(10,100,10) ) )
# which is sort of like your last notion,

All of this is untested in the absence of a reproducible example but  
you definitely should work through the examples on:

?outer
?mapply


>    }
>
> Please let me know if more detail on my code would be helpful- I was  
> just trying to keep it simple and focus on what I saw as the problem  
> at hand for now.
> Thank you for your help.
> Sincerely,
> Mike Treglia
>
> -- 
> Michael Treglia
> Applied Biodiversity Sciences NSF-IGERT Program
> Wildlife and Fisheries Sciences
> Texas A&M University
> Lab: (979)862-7245
> mlt35 at tamu.edu
> http://people.tamu.edu/~mlt35
>
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David Winsemius, MD
West Hartford, CT