Sort dataframe in a function - r

Question

I am trying to create a function which takes a dataframe and the columns by which I want to sort as arguments. This is what I have come up with:
sortDf <- function(df, columns){
df <- df[order(df[,columns]),]
return(df)
}
This is my usecase:
set.seed(24)
dataset <- matrix(sample(c(NA, 1:5), 25, replace = TRUE), 5)
df <- as.data.frame(dataset)
sortedDf <- sortDf(df, c('V1', 'V2'))
How ever I get this as a result:
V1 V2 V3 V4 V5
3 1 1 5 3 4
5 1 5 2 5 2
NA NA NA NA NA NA
NA.1 NA NA NA NA NA
NA.2 NA NA NA NA NA
NA.3 NA NA NA NA NA
1 5 2 1 2 5
4 5 2 1 2 1
NA.4 NA NA NA NA NA
2 NA 4 NA 1 4
The dataframe is kinda sorted but where does the 'NA' come from and how can I remove them? What do I do wrong? I want to sort descending. Thanks in advance.

Answer 1

We can create a different function
f1 <- function(dat, cols){
dat[do.call(order, dat[cols]),]
}
f1(df, c("V1", "V2"))
# V1 V2 V3 V4 V5
#2 1 1 2 1 3
#1 1 5 3 5 NA
#5 3 1 1 NA 1
#4 3 4 4 3 NA
#3 4 4 4 NA 4
In the OP's code, the order is applied on a data.frame instead of a vector. It can be used either separately or within do.call i.e.
df[order(df$V1, df$V2),]
# V1 V2 V3 V4 V5
#2 1 1 2 1 3
#1 1 5 3 5 NA
#5 3 1 1 NA 1
#4 3 4 4 3 NA
#3 4 4 4 NA 4
gives the same result as the OP's code. So, either it columns can be individually mentioned (which would not be easy when there are more number of columns) or use do.call.
This can also be implemented using the devel version of dplyr (soon to be released 0.6.0) with quosures. After taking the input vector, it is converted to quosures (parse_quosures) and then evaluated by unquoting (!!!) it in arrange
library(dplyr)
f2 <- function(dat, cols){
cols <- rlang::parse_quosures(paste(cols, collapse=";"))
dat %>%
arrange(!!! cols)
}
f2(df, c("V1", "V2"))
# V1 V2 V3 V4 V5
#1 1 1 2 1 3
#2 1 5 3 5 NA
#3 3 1 1 NA 1
#4 3 4 4 3 NA
#5 4 4 4 NA 4
data
set.seed(24)
df <- as.data.frame(matrix(sample(c(NA, 1:5), 25, replace = TRUE), 5))