CODEWITHSUNDEEP
rmatrixmean
humbugv
humbugv

Reputation: 25

mean of the rows where the row name is same (matrix in R)

I have a big matrix, like this:

 m:
     0   60   120   180... (column names) 
  0  2    4    5     9
  0  6    8    7     6
  0  5    2    6     4
  0  3    4    1     3
 60  4    5    3     1
 60  4    6    10    2
  .
  .
(row names)

I would like to calculate the mean of the rows, which has the same name. How can i do this in R? The outcome would look like this matrix:

k:
     0   60   120   180... (column names) 
  0  4   4,5  4,75  5,5
 60  4   5,5  6,5   1,5         
  .
  .
(row names)

I guess it is really basic, but I just can not figure out. I would appreciate a little help. Thank you!

Upvotes: 0

Views: 1193

Answers (1)

akrun
akrun

Reputation: 887118

Here is one option with aggregate from base R

aggregate(m, list(row.names(m)), mean)
#  Group.1 0  60  120 180
#1       0 4 4.5 4.75 5.5
#2      60 4 5.5 6.50 1.5

Or using tapply

tapply(m, list(row.names(m)[row(m)], colnames(m)[col(m)]), FUN = mean)

Or using by

do.call(rbind, by(m, row.names(m), FUN = colMeans))
#    0  60  120 180
#0  4 4.5 4.75 5.5
#60 4 5.5 6.50 1.5

Or with split

t(sapply(split(as.data.frame(m), row.names(m)), colMeans))

data

m <- structure(c(2, 6, 5, 3, 4, 4, 4, 8, 2, 4, 5, 6, 5, 7, 6, 1, 3, 
10, 9, 6, 4, 3, 1, 2), .Dim = c(6L, 4L), .Dimnames = list(c("0", 
"0", "0", "0", "60", "60"), c("0", "60", "120", "180")))

Upvotes: 1

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