R cannot melt data.frame

Question

I have the following data.frame, called tableMS:

     X   Y        Z        T
1  375 855 455.7259 3777.856
2  395 969 347.8306   2506.7
3  449 811 309.9512 519.8513
4  451 774  278.291 717.8705
5  453 774  278.291 717.8705
6  455 774  278.291 717.8705
7  521 697  376.734 693.8541
8  529 855 455.7259 3777.856
9  531 855 455.7259 3777.856
10 609 774  278.291 717.8705

when I try to use the function melt()

MeltTable <- melt(tableMS,id=c("X","Y"))

I get the following error:

Error in match.names(clabs, names(xi)) : 
   names do not match previous names

I struggle to understand what happens, any idea?

Edit: I generated tableMS as portion of a bigger table and the output of str(tableMS) is:

'data.frame':   10 obs. of  4 variables:
$ X: num  375 395 449 451 453 455 521 529 531 609
$ Y: num  855 969 811 774 774 774 697 855 855 774
$ Z:List of 10
  ..$ : num 456
  ..$ : num 348
  ..$ : num 310
  ..$ : num 278
  ..$ : num 278
  ..$ : num 278
  ..$ : num 377
  ..$ : num 456
  ..$ : num 456
  ..$ : num 278
$ T:List of 10
  ..$ : num 3778
  ..$ : num 2507
  ..$ : num 520
  ..$ : num 718
  ..$ : num 718
  ..$ : num 718
  ..$ : num 694
  ..$ : num 3778
  ..$ : num 3778
  ..$ : num 718

Answer 1

I had this same problem, but the cause was different. I got the same error message "names do not match previous names", but it was due to using the package dplyr.

Turns out, it is a known issue with dplyr. According to the GitHub issue, it will occur on some version of dplyr and reshape but not on others.

The output from dplyr is not just a data.frame - it inherits from data.frame. So after using dplyr to produce data this is the result:

class(data)

> [1] "tbl_df"     "tbl"        "data.frame"

melt(data, id = c("X", Y"))

>Error in match.names(clabs, names(xi)) : 
names do not match previous names

To fix this issue, I had to convert the dplyr output to a data frame. This also appears to be the recommended way to combine these packages:

data <- as.data.frame(data)
class(data)

> [1] "data.frame"

melt(data, id = c("X", "Y"))

The last block then completes without error.