ggplot mapping spatial data legend missing

Question

I am attempting my first spatial maps in ggplot:

I am quite hapy with the map and used the code:

g <-ggplot(data = world) +
  geom_sf() +
  coord_sf(crs = st_crs(4326)) +
 coord_sf(xlim = c(-10.5, -5.70), ylim = c(51.30, 55.30)) #+ xlab("Longitude") + ylab("Latitude") # sets frame

g <- g + labs(x="Longitude",y="Latitude")

g

g<- g+ geom_point(data = mapdatasize, aes(x = Y, y = X.y), size= mapdatasize$no, show.legend = TRUE) #dont know why it doesnt show legend...?
g<- g+ scale_size_continuous(name = "No of Animals") ##doesnt work neither?
g

g <- g+  annotation_scale(location = "br",style="ticks", width_hint = 0.5) + #bl is bottom left, br bottom right
  annotation_north_arrow(location = "br", which_north = "true", 
                       pad_x = unit(0, "in"), pad_y = unit(0.2, "in"),   #northarrow and scale bar
  style = north_arrow_fancy_orienteering)

g <- g + theme_classic(base_size = 15)
g<- g + theme(panel.border = element_rect(linetype = "solid", fill = NA))
g

I am missing my legend of the point sizes though. I don't know why ggplot doesn't show the legend even though I use legend = T ? My try with scale_size_continuous doesn't do it neither.

Numbers that define the size range from 1-4 I believe (no of animals at this location).

Any advice?

Answer 1

Just place the size= mapdatasize$no inside the aes():

library(giscoR)
library(ggplot2)
library(sf)
library(dplyr)
library(ggspatial)

# I need to mock your data somehow...
world <- gisco_get_countries(region = "Europe")

# Mock your animal data
mapdatasize <- world %>%
  filter(ISO3_CODE == "IRL") %>%
  st_sample(20) %>%
  st_coordinates() %>%
  as.data.frame()

names(mapdatasize) <- c("Y", "X.y")
mapdatasize$no <- sample(1:4, 20, replace = TRUE)

# End mocking data

ggplot(data = world) +
  geom_sf() +
  coord_sf(
    crs = st_crs(4326),
    xlim = c(-10.5, -5.70), ylim = c(51.30, 55.30)
  ) +
  # Here it goes!
  geom_point(data = mapdatasize, aes(x = Y, y = X.y, size = no)) +
 # Ready
  labs(x = "Longitude", y = "Latitude") +
  annotation_scale(location = "br", style = "ticks", width_hint = 0.5) +
  annotation_north_arrow(
    location = "br", which_north = "true",
    pad_x = unit(0, "in"), pad_y = unit(0.2, "in"),
    style = north_arrow_fancy_orienteering
  ) +
  theme_classic(base_size = 15) +
  theme(panel.border = element_rect(linetype = "solid", fill = NA))