How to Sort a Data.Frame with Only One Column, Without Losing Rownames

How can I sort a data.frame with only one column, without losing rownames?

You were close with your first attempt, just forgot about using drop = FALSE:

> d[order(-d$data), , drop = FALSE]
    data
yak    4
baz    3
bar    2
foo    1

How to sort each row of a data frame WITHOUT losing the column names

Store the names and apply them:

nm = names(df)
sorted_df <- as.data.frame(t(apply(df, 1, sort)))
names(sorted_df) = nm

You could compress this down to a single line if you prefer:

sorted_df = setNames(as.data.frame(t(apply(df, 1, sort))), names(df))

Is there an elegant way to reorder data frame by rownames in R

Works just fine with arrange():

library(dplyr)

d <- read.table(textConnection("
             value
gene8  0.140533602
gene6 21.129493396
gene7  0.170091711
gene3 28.101415822
gene1  0.005706749
gene2  3.157911375")) 

d %>% 
  arrange(row.names(.))
#>              value
#> gene1  0.005706749
#> gene2  3.157911375
#> gene3 28.101415822
#> gene6 21.129493396
#> gene7  0.170091711
#> gene8  0.140533602

Sorting a dataframe by a column name passed to a function

You can write the function sort.by.column using order as:

sort.by.column <- function(df, column.name) {
  df[order(df[,column.name]),]
}    

#Lets test the function

sort.by.column(df1, "Value")
#   Instrument Value
# 2          B     2
# 1          A     3
sort.by.column(df2, "Value")
#   Device Value
# 2      D     4
# 1      C     5

sort.by.column(df1, "Instrument")
#   Instrument Value
# 1          A     3
# 2          B     2
sort.by.column(df2, "Device")
#   Device Value
# 1      C     5
# 2      D     4

Data:

df1 <- data.frame(Instrument=c("A","B"),
                  Value=c(3,2))
df2 <- data.frame(Device=c("C","D"),
                  Value=c(5,4))

Explanation

It works like this. With the initialization

df <- data.frame(Instrument=c("B","A"), Value=c(3,2))
col.name <- "Instrument"

the expression

df[,col.name]

returns a 1-column subset of the data frame. The expression

order(df[,col.name])

sorts that subset, returning the indices of the rows. Finally

df[order(df[,col.name]),]

returns a row-subset of the dataframe, with the row indices in the order computed.

Use order on a single column data frame

You could add drop=FALSE and it will work with most of the cases. The default option for [ is drop=TRUE

 df1[order(df1$col1),, drop=FALSE]

In the help page for ?`[`, the default arguments can be found in the 'Usage'

 x[i, j, ... , drop = TRUE]

and the description for drop as

drop: For matrices and arrays. If ‘TRUE’ the result is coerced to
the lowest possible dimension (see the examples). This only
works for extracting elements, not for the replacement. See
‘drop’ for further details.

How to order the default column from 1 to n?

If you want to re-order the rows by row names, you can extract them with rownames, convert it to numeric and then order

df[order(as.integer(rownames(df))), ]

Or if you just want to rename them from 1:N instead of current names

rownames(df) <- NULL

How can I use the row.names attribute to order the rows of my dataframe in R?

This worked for me:

new_df <- df[ order(row.names(df)), ]

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