Sf: feature request: st_make_line

[JimShady]

https://postgis.net/docs/ST_MakeLine.html

Would work something like this:

data <- tibble(x1 = 51.4, y1 = 0.45, x2 - 54.23, y2 = 0.67)

line <- data %>%
              st_make_line(x1, y1, x2, y2)

Returning a simple feature collection (I think).

[JimShady]

Adapting this code would work:

b = graph[, c('from_lon', 'from_lat')]
names(b) = c("long", "lat")
e = graph[, c('to_lon', 'to_lat')]
names(e) = c("long", "lat")

graph$geometry = do.call(
    "c", 
    lapply(seq(nrow(b)), function(i) {
        st_sfc(
            st_linestring(
                as.matrix(
                    rbind(b[i, ], e[i, ])
                )
            ),
            crs = 4326
        )
    }))

graph = st_as_sf(graph)

[edzer]

You can use R to create LINESTRING from points, e.g.

p1 = st_point(c(51.4, 0.45))
p2 = st_point(c(54.23, 0.67))
st_linestring(rbind(p1, p2))
# LINESTRING (51.4 0.45, 54.23 0.67)

[JimShady]

I've seen a few examples along those lines @edzer , but implementing that on a dataframe?

Would it be something like this?

data$geometry <- st_linestring(rbind(
                            st_point(c(data$from_lon, data$from_lat)), 
                            st_point(data$to_lon, data$to_lat)))

[edzer]

If your data.frame has a single record, yes.

[tim-salabim]

There's also sfheaders which should work on data frames

[etiennebr]

@JimShady, you can also have a look at https://github.com/etiennebr/geotidy still experimental, but if you need these kind of constructors and don't mind using tibbles, it might work for your needs.

[JimShady]

I think I'm missing something obvious.

library(tidyverse)
library(sf)

data <- tibble(x1 = c(1,2,3,4),
               y1 = c(1,2,3,4),
               x2 = c(1,2,3,4),
               y2 = c(1,2,3,4))

data$geometry <- st_linestring(rbind(
                            st_point(c(data$x1, data$y1)), 
                            st_point(data$x2, data$y2)))

Error in is.numeric(x) && is.matrix(x) : 
  8 is an illegal number of columns for a POINT

[JimShady]

@etiennebr -- Looks very useful ! Thanks, will check it out.

[edzer]

I repeat: if your data.frame has a single record

[JimShady]

Thanks, I did read that, but my data does not, so I provided an example of code where there is more than one row of data.

Is there a method to create linestrings for each row? Doesn't seem to be?

[edzer]

st_linestring takes a matrix with points in rows; you'll have to wrangle your data into that form some way.