Is there a simpler way to reorder data by the values of a column?
I wrote this tiny little wrapper around order
, b开发者_开发技巧ut I fear my implementation is lame. I huddle in the corner, waiting for the gods of R commands or algorithmic efficiency to smite my ergonomic keyboard :-(
set.seed(1001)
height <- rnorm(6, mean = 1, sd = 0.2)
weight <- rnorm(6, mean = 100, sd = 15)
id <- 1:6
dd <- data.frame(id, height, weight)
# Here's the function I came up with
ReorderDataByColumn <- function(x, column) {
ordered.indices <- order(x[ ,paste(column)])
return(x[ordered.indices, ])
}
#And here are its results
> ReorderDataByColumn(dd, column = "height")
id height weight
4 4 0.4986928 76.09430
5 5 0.8885377 104.53967
3 3 0.9629449 86.38809
2 2 0.9644905 90.65584
6 6 0.9712881 124.51589
1 1 1.4377296 116.37253
> ReorderDataByColumn(dd, column = "weight")
id height weight
4 4 0.4986928 76.09430
3 3 0.9629449 86.38809
2 2 0.9644905 90.65584
5 5 0.8885377 104.53967
1 1 1.4377296 116.37253
6 6 0.9712881 124.51589
I'm not into the smiting business for well-formed questions. And I thought the code was readable and sensible. If you wanted to tighten it up a bit you can drop the paste() operation by using "[[" and creating the index inside "[":
ReorderDataByColumn2 <- function(x, column) {
return(x[ order( x[[column]]), ])
}
EDIT: Adding Hadley's suggestion (except I think you need do.call as well):
ReorderDataByColumn2 <- function(x, column, desc=FALSE) {
return(
x[ do.call( order, x[ , column, drop=FALSE ] ), ]
) }
You could add some error checking if you wanted:
ReorderDataByColumn2 <- function(x, column) {
if(column %in% names(x)){return(x[ order( x[[column]]), ])
}else{ cat("Column ", column, "not in dataframe ", deparse(substitute(x))) }
}
See the arrange function in plyr:
library(plyr)
arrange(mtcars, cyl)
arrange(mtcars, desc(cyl))
arrange(mtcars, vs, am)
The definition of the function is pretty simple:
arrange <- function (df, ...) {
ord <- eval(substitute(order(...)), df, parent.frame())
unrowname(df[ord, ])
}
And it works on a very similar process to subset
in base R.
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