R help - Jul 2012 - Function for ddply

Hello, all. I'm new to R and just beginning to learn to write functions. I
know I'm out of my depth posting here, and I'm sure my issue is mundane.
But here goes. I'm analyzing the American National Election Study (nes),
looking at mean values of a numeric dep_var (environ.therm) across values
of a factor (partyid3). I use ddply from plyr and wtd.mean from Hmisc. The
nes requires a weight var (wt). I use Rcmdr's plotMeans to obtain a line
chart. The following code works:

attach(nes)
obj1 = ddply(nes, .(partyid3), summarise,
  var = wtd.mean(environ.therm, wt))
print(obj1)
plotMeans(obj1$var, obj1$partyid3, error.bars="none")

Here is what happens when I write and run the function, meanN:
 meanN=function(data,x,y,w=NULL)
+  {obj1=ddply(data,.(x),summarise, var=wtd.mean(y,w))
+  print(obj1)
+  plotMeans(obj1$var, obj1$x, error.bars="none")
+ }
 meanN(nes,partyid3,environ.therm,wt)
Error in wtd.mean(y, w) : object 'w' not found

I have assigned data, x, y, and w. I'm just learning this powerful stuff.
Any help would be greatly appreciated.

Hutch Pollock

	[[alternative HTML version deleted]]

Not sure how to help you, because your example is not reproducible (does not run
on my computer).

Some comments:

Avoid using the attach function. It is way better to use the data argument
available in most functions.

The summarise function is designed for interactive use. You should probably
write your own .FUN function if you are calling ddply within your own function. 
See the help for ddply for examples of how to do that.
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Hutch Pollock <hutchpollock at gmail.com> wrote:
>Hello, all. I'm new to R and just beginning to learn to write
>functions. I
>know I'm out of my depth posting here, and I'm sure my issue is
>mundane.
>But here goes. I'm analyzing the American National Election Study
>(nes),
>looking at mean values of a numeric dep_var (environ.therm) across
>values
>of a factor (partyid3). I use ddply from plyr and wtd.mean from Hmisc.
>The
>nes requires a weight var (wt). I use Rcmdr's plotMeans to obtain a
>line
>chart. The following code works:
>
>attach(nes)
>obj1 = ddply(nes, .(partyid3), summarise,
>  var = wtd.mean(environ.therm, wt))
>print(obj1)
>plotMeans(obj1$var, obj1$partyid3, error.bars="none")
>
>Here is what happens when I write and run the function, meanN:
> meanN=function(data,x,y,w=NULL)
>+  {obj1=ddply(data,.(x),summarise, var=wtd.mean(y,w))
>+  print(obj1)
>+  plotMeans(obj1$var, obj1$x, error.bars="none")
>+ }
> meanN(nes,partyid3,environ.therm,wt)
>Error in wtd.mean(y, w) : object 'w' not found
>
>I have assigned data, x, y, and w. I'm just learning this powerful
>stuff.
>Any help would be greatly appreciated.
>
>Hutch Pollock
>
>	[[alternative HTML version deleted]]
>
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