Cannot output spatial dataframe to .shp - r

Question

I've used gConvexHull() to create a home range polygon that is classed as an SP polygon. In order to output as an .shp file, I converted it to a SpatialPolygonsDataFrame and its new class is "sf" "data.frame".
But when I try to output it using writeOGR(), it comes up with the error message:
Error in writeOGR(obj = HRDF, dsn = "C:/Users/RKirton/Documents/Data files", :
inherits(obj, "Spatial") is not TRUE
I also tried st_write() and got this new error message:
Error in CPL_write_ogr(obj, dsn, layer, driver, as.character(dataset_options), :
argument dsn, layer or driver not of length 1.
I'm fairly new to R and am unsure how to resolve these error messages.
Here is my code:
for(i in 1:length(unique(mydata$ID))) {
hunt <- mydata[which(mydata$Season2 == "Hunt" & mydata$ID ==
unique(mydata$ID)[i]), ]
hunt_spdf <- SpatialPointsDataFrame(coords = cbind(hunt$X, hunt$Y), data =
hunt, proj4string = CRS("+init=epsg:32614"))
HR = gConvexHull(hunt_spdf, byid = FALSE)
plot(hunt_spdf)
plot(HR, add = TRUE)
HRDF = SpatialPolygonsDataFrame(HR, data = data.frame(IDs="Deer_HHR"))
HRDF = st_as_sf(HR)
HRDF
HRDF$NEWCOL = "ID"
HRDF
st_write(obj = HRDF, dsn="C:/Users/RKirton/Documents/Data files",
layer=paste0('DeerHHR_', hunt$ID), driver="ESRI Shapefile")
}

Answer 1

If you want to tag someone in a comment you need to use the # symbol, as in #SymbolixAU, then they'll get notified.
Also, it's hard to find the errors in your code without having a reproducible example.
To try and help, here's a working example of creating an sf object from a data.frame, then finding the convex hull, then saving the .shp file(s) to a directory. If you want specific help you need to supply some data for others to work with.
This example is only using sf objects, not sp
library(sf)
library(sfheaders)
## An example data.frame
df <- data.frame(
id = c( rep(1, 15), rep(2, 11))
, x = rnorm(26)
, y = rnorm(26)
)
sf <- sfheaders::sf_multipoint(obj = df, multipoint_id = "id", x = "x", y = "y")
sf <- sf::st_set_crs( sf, 32614 )
sf
# Simple feature collection with 2 features and 1 field
# geometry type: MULTIPOINT
# dimension: XY
# bbox: xmin: 1 ymin: 1 xmax: 26 ymax: 26
# z_range: zmin: NA zmax: NA
# m_range: mmin: NA mmax: NA
# epsg (SRID): 32614
# proj4string: +proj=utm +zone=14 +datum=WGS84 +units=m +no_defs
# id geometry
# 1 1 MULTIPOINT (1 26, 2 25, 3 2...
# 2 2 MULTIPOINT (16 11, 17 10, 1...
sf_hull <- sf::st_convex_hull( sf )
sf_hull
sf::st_write( obj = sf_hull, dsn = "~/Desktop/my_hull_dir/my_hull.shp")