The reason I think it is not continuous is because this data frame comes from merging 2 cleaned and subset data frames. Here is the str()
> str(df.main)
'data.frame': 72 obs. of 4 variables:
$ Column.1 : Factor w/ 2367 levels "1010477","1010488",..: 1 2 20 21 66 72 73 77 78 87 ...
$ Column.4.y: Factor w/ 2033 levels "","2 Seat Reclining Power Sofa",..: 2019 1519 1653 1652 1505 2 2008 2 2007 1213 ...
$ Column.6.x: Factor w/ 26 levels "-1","-2","-4",..: 5 5 12 5 5 12 16 16 5 5 ...
$ Column.6.y: Factor w/ 46 levels "-1","-2","-6",..: 6 6 32 26 36 26 32 40 16 16 ...