增加点大小或更改GGplot的形状

Question

我正在绘制一个如下所示的图，并且想要增加点的大小，更改形状，或者最好使其成为一个连续的点。

当我尝试使用geom_point时，它会删除这些点的颜色，但确实会使它们变大。

library(rayshader)
library(sp)
library(raster)
library(scales)
library(rgdal)
library(tidyverse)
library(viridis)
#Data from NY Times
mask = read_csv("mask-use-by-county_ed.csv")

maskgg = ggplot(mask) +
  geom_raster(aes(x=ALWAYS_MASK,y=PERCENT_COLLEGE,fill=COVID_CASES)) +
  scale_x_continuous("ALWAYS WEARS MASK",expand=c(0,0),breaks=seq(0,100,10)) +
  scale_y_continuous("PERCENT COLLEGE",expand=c(0,0),breaks=seq(0,60,10),limits=c(0,60)) +
  scale_fill_viridis_c() +
  ggtitle("COVID CASES BY MASK USE AND EDUCATION") +
  labs(caption = "Data Source: NY TIMES")
maskgg

plot_gg(maskgg, multicore=TRUE,height=5,width=6,scale=500)

3D Plot of Data