Transpose rows and columns in data frame using first column entries as colnames in new R data frame

Question

My data frame df looks like this:

      ID     A   B   C    D...Z
1   name1    4   6   7    8...
2   name2    5   8   3    5...
...
50 name50    4   6   7    8...

This is what I need:

   ID   name1   name2 ...name50 
1  A      4      5    ...  4
2  B      6      8    ...  6
etc.

I have tried the transpose command, as.data.frame(t(df)), but the index number for the rows (1,2,...50) becomes the column names, which I do not want. I would like to use the first column in the old data frame (name1, name2, ...) to become the column names of the new data frame. I also lose the index numbers for the rows, which I need.

Main problem is that df has about 15k rows, and 45 columns, so swapping rows and columns using brute force, is not that simple.

Yes, I need the data in a data frame.

Answer 1

library(tibble)
library(dplyr)

df %>%
  t() %>%
  as.data.frame(stringsAsFactors = F) %>%
  rownames_to_column("value") %>%
  `colnames<-`(.[1,]) %>%
  .[-1,] %>%
  `rownames<-`(NULL)

Output is:

  ID name1 name2 name50
1  A     4     5      4
2  B     6     8      6
3  C     7     3      7
4  D     8     5      8

Sample data:

df <- structure(list(ID = c("name1", "name2", "name50"), A = c(4L, 
5L, 4L), B = c(6L, 8L, 6L), C = c(7L, 3L, 7L), D = c(8L, 5L, 
8L)), .Names = c("ID", "A", "B", "C", "D"), class = "data.frame", row.names = c(NA, 
-3L))