R: invalid subscript type 'list'

Question

I'm trying to use the indices of a sorted column of a dataset. I want to reorder the entire dataset by one sorted column.

area.sort<-sort(xsample$area1, index.return=TRUE)[2]

The output is a list, so I can't use it index through the whole dataset.

Error in xj[i] : invalid subscript type 'list'

Someone suggested using unlist but I can't get rid of the ix*. Any ideas? Thanks

> area.sort<-unlist(area.sort)

 ix1   ix2   ix3   ix4   ix5   ix6   ix7   ix8   ix9  ix10  ix11  ix12  ix13 
  45    96    92    80    53    54    24    21    63    81    40    66    64 

Answer 1

The call to sort with index.return=TRUE returns a list with two components: x and ix. Indexing with [2] returns a subset of the list - still a list.

If you index using [[2]] it should work better. That returns the element in the list. But indexing using $ix is perhaps a bit clearer.

But then again, if you only need the sorted indices, you should call order instead of sort...