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Given a data.frame:
foo <- data.frame(ID=1:10, x=1:10)
rownames(foo) <- LETTERS[1:10]
I would like to reorder a subset of rows, defined by their row names. However, I would like to swap the row names of foo as well. I can do
sel <- c("D", "H") # rows to reorder
foo[sel,] <- foo[rev(sel),]
sel.wh <- match(sel, rownames(foo))
rownames(foo)[sel.wh] <- rownames(foo)[rev(sel.wh)]
but that is long and complicated. Is there a simpler way?
469
To sort a data frame in R, use the order( ) function. By default, sorting is ASCENDING. Prepend the sorting variable by a minus sign to indicate DESCENDING order.
The arrange() function lets you reorder the rows of a tibble. It takes a tibble, followed by the unquoted names of columns. For example, to sort in ascending order of the values of column x , then (where there is a tie in x ) by descending order of values of y , you would write the following.
Subsetting in R is a useful indexing feature for accessing object elements. It can be used to select and filter variables and observations. You can use brackets to select rows and columns from your dataframe.
We can replace the sel values in rownames with the reverse of sel.
x <- rownames(foo)
foo[replace(x, x %in% sel, rev(sel)), ]
# ID x
#A 1 1
#B 2 2
#C 3 3
#H 8 8
#E 5 5
#F 6 6
#G 7 7
#D 4 4
#I 9 9
#J 10 10
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