convert object of class “dist” into data frame in r

Question

if possible to convert a data frame to an object of class \"dist\" is it possible to do just the opposite? convert class \"dist\" to data frame? for example

< dist(ha

Answer 1

Here's another approach that avoids melt() and as.matrix() ... it'd be nice to avoid subset() too, but I'll leave that as a homework exercise

dist.to.df <- function(d){
  size <- attr(d, "Size")
  return(
    data.frame(
      subset(expand.grid(row=2:size, col=1:(size-1)), row > col),
      distance=as.numeric(d),
      row.names = NULL
    )
  )
}

which gives...

library(maps)
data(us.cities)
d <- dist(head(us.cities[c("lat", "long")]))
dist.to.df(d)
##    row col  distance
## 1    2   1 20.160489
## 2    3   1 23.139853
## 3    4   1 15.584303
## 4    5   1 27.880674
## 5    6   1 26.331187
## 6    3   2 40.874243
## 7    4   2  9.865374
## 8    5   2  7.882037
## 9    6   2 41.720457
## 10   4   3 38.579820
## 11   5   3 48.707100
## 12   6   3  6.900101
## 13   5   4 15.189882
## 14   6   4 41.036931
## 15   6   5 49.328558