Add vertical polylines of specific length to contiguous polygons in R - r

Question

I'm attempting to pro-grammatically add multiple vertical polylines of specific length to contiguous polygons in R. The number and length of the polylines should be specified by the user and can range from 1 to 8 polylines and 5000 to 10000 feet long per contiguous polygons. How can I achieve this in R?
I'm able to do this manually by the use of the mapedit package for a couple of polygons but I would like to automate the process for several thousand contiguous polygons.
# Load required libraries
library(mapedit)
library(mapview)
library(dplyr)
library(sp)
# Sample polygons and polylines
geometry = structure(list(structure(list(structure(c(8.769563, 8.769563,
8.770507, 8.770507, 8.769563, 50.815273, 50.815714, 50.815714,
50.815273, 50.815273), .Dim = c(5L, 2L))), class = c("XY", "POLYGON",
"sfg")), structure(list(structure(c(8.769568, 8.769568, 8.770507,
8.770507, 8.769568, 50.814852, 50.81527, 50.81527, 50.814852,
50.814852), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.769568, 8.769568, 8.770502,
8.770502, 8.769568, 50.814412, 50.814849, 50.814849, 50.814412,
50.814412), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.769568, 8.769568, 8.770502,
8.770502, 8.769568, 50.814005, 50.814408, 50.814408, 50.814005,
50.814005), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.770502, 8.770502, 8.771301,
8.771301, 8.770502, 50.815273, 50.815717, 50.815717, 50.815273,
50.815273), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.770518, 8.770518, 8.771301,
8.771301, 8.770518, 50.814852, 50.81527, 50.81527, 50.814852,
50.814852), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.770507, 8.770507, 8.771301,
8.771301, 8.770507, 50.814408, 50.814849, 50.814849, 50.814408,
50.814408), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(list(structure(c(8.770507, 8.770507, 8.771296,
8.771296, 8.770507, 50.814005, 50.814405, 50.814405, 50.814005,
50.814005), .Dim = c(5L, 2L))), class = c("XY", "POLYGON", "sfg"
)), structure(c(8.769794, 8.769783, 50.814785, 50.814076), .Dim = c(2L,
2L), class = c("XY", "LINESTRING", "sfg")), structure(c(8.770051,
8.770035, 50.814785, 50.814069), .Dim = c(2L, 2L), class = c("XY",
"LINESTRING", "sfg")), structure(c(8.770271, 8.77026, 50.814781,
50.814076), .Dim = c(2L, 2L), class = c("XY", "LINESTRING", "sfg"
))), class = c("sfc_GEOMETRY", "sfc"), precision = 0, bbox = structure(c(xmin = 8.769563,
ymin = 50.814005, xmax = 8.771301, ymax = 50.815717), class = "bbox"), crs = structure(list(
epsg = 4326L, proj4string = "+proj=longlat +datum=WGS84 +no_defs"), class = "crs"), classes = c("POLYGON",
"POLYGON", "POLYGON", "POLYGON", "POLYGON", "POLYGON", "POLYGON",
"POLYGON", "LINESTRING", "LINESTRING", "LINESTRING"), n_empty = 0L)
# Visualize geometry
mapview(geometry)
I attempted to create regularly sampled points via the spsample function inside the polygons and connecting them by lines but was unsuccessful. appreciate any help I can get.

Answer 1

Here's one way to create lines given a polygon. It's probably not exactly what you want, since your request is quite specific, but hopefully the code is generic enough that you cn adapt it.
library(sf)
library(purrr)
polygon <- st_polygon(list(matrix(c(1,1,2,2,1,1,0,0,1,1), ncol = 2)))
# use polygon bounding box to o compute line parameters
bb <- st_bbox(polygon)
number_of_lines <- 5
line_length <- (bb[["ymax"]] - bb[["ymin"]]) / 1.2
y_offset <- bb[["ymin"]] + (bb[["ymax"]] - bb[["ymin"]] - line_length) / 2
# compute coordinates
xs <- seq(bb[["xmin"]], bb[["xmax"]], length.out = number_of_lines)
ys <- bb[["ymin"]] + line_length
# create a linestring
lines <- purrr::map2(xs, ys, ~st_linestring(matrix(c(.x, .x, .y,y_offset), ncol = 2))) %>% st_sfc(crs = st_crs(polygon))
# view
plot(polygon)
plot(lines, col = 2, add = TRUE)