Change row order in a matrix/dataframe

Question

I need to change/invert rows in my data frame, not transposing the data but moving the bottom row to the top and so on. If the data frame was:

1 2 3 
4 5 6
7         


        

Answer 1

Encounter this problem today and here I am providing another solution for your interests.

m <- matrix(1:9, ncol=3, byrow=TRUE)    
apply(m,2,rev)

Answer 2

I would reverse the rows an index starting with the number of rows, along this line

revdata <-  thedata[dim(thedata)[1L]:1,]

Answer 3

Veeery late, but this seems to be working fast, does not need any extra packages and is simple:

for(i in 1:ncol(matrix)) {matrix[,i] = rev(matrix[,i])}

I guess that for frequent use, one would make a function out of it. Tested with R v=3.3.1.

Answer 4

We can reverse the order of row.names (for data.frame only):

# create data.frame
m <- matrix(1:9, ncol=3, byrow=TRUE)
df_m <- data.frame(m)

#reverse
df_m[rev(rownames(df_m)), ]

#   X1 X2 X3
# 3  7  8  9
# 2  4  5  6
# 1  1  2  3

Answer 5

You can reverse the order of a data.frame using the dplyr package:

iris %>% arrange(-row_number())

Or without using the pipe-operator by doing

arrange(iris, -row_number())

Answer 6

I think this is the simplest way:

MyMatrix = matrix(1:20, ncol = 2)
MyMatrix[ nrow(MyMatrix):1, ]

If you want to reverse the columns, just do

MyMatrix[ , ncol(MyMatrix):1 ]