Hi all,

I would like to invoke a function that takes multiple arguments (some of
which are specified columns in the data frame, and others that are
independent of the data frame) on split parts of a data frame, how do I do
this?

For example, let's say I have a data frame
>fitness_data
name  height  weight  country
rob      5.8        200      usa
nancy  5.5        140      germany
jen       5.6        150      usa
clark     5.10      210     germany
matt     5.9         280     canada
ralph    6           270     canada
...
...

Now let us say I have a function,  my_func(h, w, noise, dir), which takes as
input:
(1) a vector of heights
(2) a vector of weights
(3) a user-input numeric "noise" value
(4) a user-input string "dir" for the directory to output the end result of
the function to

This function does some calculations on the input data and outputs a
dataframe that is then written to a file in the "dir" directory.

If I want to apply this function to data grouped by each country in the
"fitness_data" dataframe, how would I do this? I tried looking through the
mailing archives, but couldn't nail down the solution. I tried something
like

split(mapply( function(a,b,c,d) my_func(fitness_data$h, fitness_data$w, 2.5,
my_directory)), fitness_data$country)

but this considered fitness_data$h, and fitness_data$w in each single row
for a country, rather than a vector of heights or weights across all rows
corresponding to that country.

Thanks!

	[[alternative HTML version deleted]]


