> -----Original Message-----
> From: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] On Behalf Of chipmaney
> Sent: Thursday, August 26, 2010 3:00 PM
> To: r-help@r-project.org
> Subject: [R] Non-standard sorts on vectors
>
>
> I have a dataset I need to sort:
>
> test.df<-data.frame(Zone=c("Floodplain", "Lake",
> "Shoreline"),Cover=c(50,60,70))
>
> However, I don't want it sorted ascending/descending but in
> an order that I
> define via a vector:
>
> sort.v<-data.frame(c("Lake","Shoreline","Floodplain"))
>
> I realize I could probably just create the vector of
> [factors] in the order
> I want, then assign the value:
>
> sort.v$Cover<-test.df$Cover
>
> However, this is inefficient.
What is your measure of inefficiency?
If you always want results in this order
I would recommend you convert the Cover column
to a factor with the levels in the order that you
want. E.g.,
> test.df <- data.frame(
Zone=c("Floodplain","Lake","Floodplain","Shoreline","Lake","Shoreline"),
Cover=c(45, 65, 49, 75, 67, 77),
Year=c(1977, 1980, 1990, 1985, 1995, 2010))
> test.df$Zone <- factor(test.df$Zone,
levels=c("Lake","Shoreline","Floodplain"))
> # that call to factor could have been in the original call to
> # to data.frame(), but if you made the data.frame with read.table()
> # then it is easiest to make the factors in a separate step.
> test.df
Zone Cover Year
1 Floodplain 45 1977
2 Lake 65 1980
3 Floodplain 49 1990
4 Shoreline 75 1985
5 Lake 67 1995
6 Shoreline 77 2010
Now it sorts the way you want and tables, model summaries,
plots, and lots of other things will be in the order
that you like:
> test.df[order(test.df$Zone),]
Zone Cover Year
2 Lake 65 1980
5 Lake 67 1995
4 Shoreline 75 1985
6 Shoreline 77 2010
1 Floodplain 45 1977
3 Floodplain 49 1990
> table(test.df$Zone)
Lake Shoreline Floodplain
2 2 2
> lm(data=test.df, Cover ~ Zone - 1)
Call:
lm(formula = Cover ~ Zone - 1, data = test.df)
Coefficients:
ZoneLake ZoneShoreline ZoneFloodplain
66 76 47
> library(lattice)
> xyplot(data=test.df, Cover ~ Year | Zone)
Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com
> Is there source code or a
> syntactical trick
> that will do the same more efficiently? Note: I have
> investigated order()
> and sort(), but neither seems to have an argument for
> defining the sorting
> order.
>
> Thanks in advance, Chipper
>
> --
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2340431p2340431.html
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>
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