Check directional netwok

The check of directionality of animal networks is not working properly.

The following should give an error.

library(mapMCDA)
df <- data.frame(
  orig = "A",
  dest = "B",
  olon = 1,
  olat = 1,
  dlon = 2,
  dlat = 2,
  stringsAsFactors = FALSE
)

tf <- tempfile(fileext = ".csv")
write.csv(df, file = tf, row.names = FALSE)
read_network(tf)
#> IGRAPH e7c95ba DN-- 2 1 -- 
#> + attr: name (v/c)
#> + edge from e7c95ba (vertex names):
#> [1] A->B

On the other hand, we might relax this condition and give a warning instead.

^{Created on 2020-04-29 by the reprex package (v0.3.0)}