[R] Why can't I access this type?

[Henric Winell]

On 2015-03-25 09:40, Patrick Connolly wrote:

> On Sun, 22-Mar-2015 at 08:06AM -0800, John Kane wrote:
>
> |> Well, first off, you have no variable called "Name".  You have lost
> |> the state names as they are rownames in the matrix state.x77 and
> |> not a variable.
> |>
> |> Try this. It's ugly and I have no idea why I had to do a cbind()
>
> You don't have to use cbind
>
> |> but it seems to work. Personally I find subset easier to read than
> |> the indexing approach.
>
> |> state  <-  rownames(state.x77)
> |> all.states <- as.data.frame(state.x77)
> |> all.states  <-  cbind(state, all.states) ### ?????
>
> You don't have to use cbind()
>
> all.states  <- within(as.data.frame(state.x77), state <- rownames(state.x77))
>
> but I think cbind is simpler to read.
>
> |>
> |> coldstates  <-   subset(all.states, all.states$Frost > 50,
> |>                         select = c("state","Frost") )

I find the indexing approach

coldstates <- all.states[all.states$Frost > 150, c("state","Frost")]

to be the most direct and obvious solution.

> Tidier, even more so than subset():
>
> require(dplyr)
> coldstates <- all.states %>% filter(Frost > 150) %>% select(state, Frost)
>
> Or, easier to see what's happening:
>
> coldstates <- all.states %>%
>    filter(Frost > 150) %>%
>    select(state, Frost)

Well...  Opinions may perhaps differ, but apart from '%>%' being 
butt-ugly it's also fairly slow:

 > library("microbenchmark")
 > microbenchmark(
+     subset(all.states, all.states$Frost > 150, select = 
c("state","Frost")),
+     all.states[all.states$Frost > 150, c("state","Frost")],
+     all.states %>% filter(Frost > 150) %>% select(state, Frost),
+     times = 1000L
+ )
Unit: microseconds
 
    expr
  subset(all.states, all.states$Frost > 150, select = c("state", 
"Frost"))
                        all.states[all.states$Frost > 150, c("state", 
"Frost")]
                    all.states %>% filter(Frost > 150) %>% select(state, 
Frost)
       min       lq      mean    median        uq      max neval cld
   139.112  148.673  163.3960  159.1760  170.7895 1763.200  1000  b
   104.039  111.973  127.2138  120.4395  128.6640 1381.809  1000 a
  1010.076 1033.519 1133.1469 1107.8480 1175.1800 2932.206  1000   c

Of course, this doesn't matter for interactive one-off use.  But lately 
I've seen examples of the '%>%' operator creeping into functions in 
packages.  However, it would be nice to see a fast pipe operator as part 
of base R.


Henric Winell



>
>
> |>
> |>
> |> John Kane
> |> Kingston ON Canada
> |>
> |>
> |> > -----Original Message-----
> |> > From: yoursurrogategod at gmail.com
> |> > Sent: Sun, 22 Mar 2015 10:39:03 -0400
> |> > To: r-help at r-project.org
> |> > Subject: [R] Why can't I access this type?
> |> >
> |> > Hi, I'm just learning my way around R.  I got a bunch of states and would
> |> > like to access to get all of the ones where it's cold.  But when I do the
> |> > following, I will get the following error:
> |> >
> |> >> all.states <- as.data.frame(state.x77)
> |> >> cold.states <- all.states[all.states$Frost > 150, c("Name", "Frost")]
> |> > Error in `[.data.frame`(all.states, all.states$Frost > 150, c("Name",  :
> |> >   undefined columns selected
> |> >
> |> > I don't get it.  When I look at all.states, this is what I see:
> |> >
> |> >> str(all.states)
> |> > 'data.frame':   50 obs. of  8 variables:
> |> >  $ Population: num  3615 365 2212 2110 21198 ...
> |> >  $ Income    : num  3624 6315 4530 3378 5114 ...
> |> >  $ Illiteracy: num  2.1 1.5 1.8 1.9 1.1 0.7 1.1 0.9 1.3 2 ...
> |> >  $ Life Exp  : num  69 69.3 70.5 70.7 71.7 ...
> |> >  $ Murder    : num  15.1 11.3 7.8 10.1 10.3 6.8 3.1 6.2 10.7 13.9 ...
> |> >  $ HS Grad   : num  41.3 66.7 58.1 39.9 62.6 63.9 56 54.6 52.6 40.6 ...
> |> >  $ Frost     : num  20 152 15 65 20 166 139 103 11 60 ...
> |> >  $ Area      : num  50708 566432 113417 51945 156361 ...
> |> >
> |> > What am I messing up?
> |> >
> |> > 	[[alternative HTML version deleted]]
> |> >
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>