Connecting two sets of coordinates to create lines using sf/mapview - r

Question

I have a dataset where a bird captured in one location (Blong, Blat) then encountered again in another (Elong, Elat). These coordinates are in a lat/long format, and I'd like to connect the capture and encounter locations with a line and plot them in mapview.
In the data below, each row is an individual bird with its capture/encounter coordinates, and the flyway that it belongs to (which I would like to use to color the lines in mapview.
dat <- structure(list(Blong = c(-75.58333, -76.08333, -81.08333, -94.25,
-75.41667, -99.41667, -77.41667, -116.08333, -89.58333, -77.58333
), Blat = c(37.58333, 40.58333, 42.75, 41.91667, 38.25, 28.25,
38.91667, 43.58333, 44.25, 38.91667), Elong = c(-65.91667, -75.75,
-80.58333, -95.41667, -73.58333, -89.41667, -77.58333, -116.41667,
-96.41667, -77.41667), Elat = c(45.91667, 40.58333, 42.75, 29.75,
45.58333, 48.25, 38.75, 43.58333, 34.08333, 38.91667), Flyway = structure(c(2L,
2L, 2L, 1L, 2L, 2L, 2L, 3L, 2L, 2L), .Label = c("Central", "Eastern",
"West"), class = "factor")), .Names = c("Blong", "Blat", "Elong",
"Elat", "Flyway"), row.names = c(NA, -10L), class = c("tbl_df",
"tbl", "data.frame"))
A look at the data:
# A tibble: 10 x 5
Blong Blat Elong Elat Flyway
<dbl> <dbl> <dbl> <dbl> <fct>
1 -75.6 37.6 -65.9 45.9 Eastern
2 -76.1 40.6 -75.8 40.6 Eastern
3 -81.1 42.8 -80.6 42.8 Eastern
4 -94.2 41.9 -95.4 29.8 Central
5 -75.4 38.2 -73.6 45.6 Eastern
6 -99.4 28.2 -89.4 48.2 Eastern
7 -77.4 38.9 -77.6 38.8 Eastern
8 -116. 43.6 -116. 43.6 West
9 -89.6 44.2 -96.4 34.1 Eastern
10 -77.6 38.9 -77.4 38.9 Eastern
I've looked a few examples, but haven't found one that looks quite like my data set.

Answer 1

The tricky thing is to create a valid LINESTRING object from the coordinate pairs in wide format. sf expects linestring coordinates in rows of a matrix. Here's a way that works. The sfc column of a sf object is a list so here we use lapply to loop over the rows of the data you provided.
library(sf)
library(mapview)
b = dat[, c("Blong", "Blat")]
names(b) = c("long", "lat")
e = dat[, c("Elong", "Elat")]
names(e) = c("long", "lat")
dat$geometry = do.call(
"c",
lapply(seq(nrow(b)), function(i) {
st_sfc(
st_linestring(
as.matrix(
rbind(b[i, ], e[i, ])
)
),
crs = 4326
)
}))
dat_sf = st_as_sf(dat)
mapview(dat_sf, zcol = "Flyway")