How to find the geom_line control points in ggplot?

[isabelle]

I was able to find the geom_curve control points in ggplot using the answer on this question:

How to find the geom_curve control points in ggplot

I am now wondering how to apply this same function to geom_line to obtain all the control points along the geom_line I created on my ggplot.

b$data[[1]] gives the starting and ending points and
p$layers[[1]]$geom_params gives the curve information (angle, curvature, ...).

But how do I find all the coordinates/points along the geom_line so I can reproduce the line with those points?

 C <- ggplot() +
    geom_sf(data = world, fill = "grey69", size = 0.1, colour = "transparent") +
    scale_x_continuous(limits = c(-180, 180), breaks = seq(-180, 180, by = 40)) +
    scale_y_continuous(limits = c(-90, 90), breaks = seq(-90, 90, by = 30)) +
    coord_sf(expand = FALSE) + 
    labs(x = "Longitude", y = "Latitude") +
    geom_sf(data = world, color = "grey87", fill = "grey87", size = 0.1) + 
    geom_line(aes(c(19, 6),c(-32,-40)), 
            lineend = "round", size = 0.4, col = "gray20", linetype = "solid", alpha = 0.6)

[Jwvz001]

Hi @isabelle ,

First, welcome to this forum!

Maybe you already solved this issue over the last days. I am not entirely sure what you are after. Mathematically a straight line is determined by its start and end point. First, you could use geom_curve() instead of geom_line().
For geospatial calculations things are a bit different for 'straight' projections. Here you could take look at the geosphere::gcIntermediate() function of the geosphere-package. This function uses the GreatCircle intersection and you can specify how many intermediate points should be taken and returned.

I hope this helps .

JW