[R] parameterization question

[William Dunlap]

You could try using the non-formula interface to aggregate.

Note that the following two calls to aggregate are equivalent but
the second (using the non-formula interface) makes the response column
a variable:

  > df <- data.frame(Y1=1:10, Y2=101:110, Group=rep(letters[1:3], c(3,3,4)))
  > aggregate(Y1 ~ Group, data=df, FUN=sum)
    Group Y1
  1     a  6
  2     b 15
  3     c 34
  > responseColumn <- "Y1"
  > aggregate(df[responseColumn], by=df["Group"], FUN=sum)
    Group Y1
  1     a  6
  2     b 15
  3     c 34

Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Sep 5, 2014 at 10:57 AM, Dale Garman <garman.dale at gmail.com> wrote:
> How can I parameterize the function call to aggregate() below with colx (a
> character string) in the following code?   That is, replace both if
> statements with aaa <- aggregate(colx_something, data=tidy[grpyrs,],sum).
> I've tried a couple of ideas for "colx_something" but get an R-error each
> time.  Been using R for 5-6 months and want to expand my knowledge.
>
> explain_causes <- function(spread, colx, peakyears) {
>     for(i in peakyears) {
>         grpyrs <- tidy$year >= (i-spread) & tidy$year <= (i+spread)
>         if(colx == "harm")
>             aaa <- aggregate(harm ~ EVTYPE, data=tidy[grpyrs,],sum)
>         if(colx == "damage")
>             aaa <- aggregate(damage ~ EVTYPE, data=tidy[grpyrs,],sum)
>         .
>         .
>         .
>     }
> }
>
> # "harm" is a column var in tidy dataframe
> explain_causes(0,"harm",c(1953,1965,1974,1979,1984,1995,1998,2011))
>
> # "damage" is a column var in tidy dataframe
> explain_causes(0,"damage",c(2005,2006))
>
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>
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