among-group distances

pw_dist.rmd

```r
inter_grp_dist <- function(combo, M, group_map){
  vals <-  M[group_map == combo[1], group_map == combo[2]] 
  list( combo=paste(combo, collapse="-"), mean=mean(vals), var=var(as.vector(vals)) )
 }

within_grp_dist <- function(grp, M , group_map){
  vals <- M[group_map == grp, group_map==grp]
  vals <- vals[lower.tri(vals)]
  list( combo=grp, mean=mean(vals), var=var(vals) )
}

group_dists <- function(dm, group_map){
 between <- combn(unique(spp), 2, FUN=function(x) inter_grp_dist(x, dm, group_map), simplify=FALSE)
 within <- lapply(unique(spp), within_grp_dist, dm, group_map)  
 do.call(rbind.data.frame, c(within, between))
}

group_dists(M, spp)
```
```sh
   combo       mean          var
2      A 0.01359186 2.788514e-05
21     B 0.01359344 2.223939e-05
3      C 0.01178926 1.598179e-05
4    A-B 0.01412923 2.022738e-05
5    A-C 0.01310000 2.477668e-05
6    B-C 0.01229028 2.399985e-05

```