R ggplot geom_raster增加行高以避免点重叠

Question

ggplot和R专家，

一个新手。我有一个用例，正在使用geom_raster进行优化。

这是可复制的R脚本：

require(ggplot2)
library(ggrepel)
# Create the data frame.
sales_data <- data.frame(
  emp_name = rep(c("Sam", "Dave", "John", "Harry", "Clark", "Kent", "Kenneth", "Richard", "Clement", "Toby", "Jonathan"), times = 50), 
  month = as.factor(rep(c("Jan", "Feb", "Mar", "Jan", "Feb", "Mar", "Jan", "Feb", "Mar", "Jan", "Jan"), times = 50)),
  dept_name = as.factor(rep(c("Production", "Services", "Support", "Support", "Services", "Production", "Production", "Support", "Support", "Support", "Production"), times = 50)), 
  revenue = rep(c(100, 200, 300, 400, 500, 600, 500, 400, 300, 200, 500), times = 50),
  status = rep(c("Low", "Medium", "Medium", "High", "Very High", "Very High", "Very High", "High", "Medium", "Medium", "Low"), times = 50)
)

sales_data$month <- factor(sales_data$month, levels = c("Jan", "Feb", "Mar"))
month_vector <- levels(sales_data$month)
number_of_enteries <- nrow(sales_data)

sales_data$status <- factor(sales_data$status, levels = c("Low", "Medium", "High", "Very High"))
sales_data$month <- as.integer(sales_data$month)

ggplot(sales_data, aes(x = month, y = dept_name)) +
  geom_raster(data = expand.grid(sales_data$month, sales_data$dept_name),
              aes(x = Var1, y = Var2, width=1, height=1), fill = NA, col = 'gray50', lty = 1) + #default width and height is 1
  #SAFE: geom_point(aes(size = revenue, col = revenue), 
  #           shape = 16, position = position_jitter(seed = 0), show.legend = F) +
  geom_point(aes(size = status, colour = cut(revenue, c(-Inf, 199, 301, Inf)) ), 
             shape = 16, position = position_jitter(seed = 0), show.legend = F) +
  scale_color_manual(name = "revenue", 
                     values = c("(-Inf,199]" = "red",
                                "(199,301]" = "#ffbf00", #amber
                                "(301, Inf]" = "green") ) +
  geom_text(aes(label = revenue), size=4, vjust = 1.6, position = position_jitter(seed = 0)) + #try with geom_text

  theme_bw() +
  theme(
    axis.title = element_blank(),
    axis.ticks = element_blank(),
    plot.background = element_blank(), 
    axis.line = element_blank(), 
    panel.border = element_blank(), 
    panel.grid = element_blank(),

    axis.text = element_text(colour = "blue", face = "plain", size =11)
  ) +

  scale_x_continuous(limits=c(0.5,3.5), expand = c(0,0), breaks = 1:length(month_vector), labels = month_vector) +

  # Remove extra whitespace from y-axis so lines are against the axis
  scale_y_discrete(expand = c(0,0)) +
  # Add straight lines at each factor level, shifted left/down so they're between values
  geom_hline(yintercept = as.numeric(sales_data$dept_name) + 0.5) +
  geom_vline(xintercept = as.numeric(sales_data$month) - 0.5, color = "grey")

输出图： 可以看到，有很多重叠。 我在这里有两个问题：

1. 如何增加行的高度，以便为geom_point提供更多空间。在这种情况下可以使用facet_grid吗？我不确定在这里如何以及如何使用facet_grid

2. 除了position_jitter以外，还有其他方法可以随机绘制气泡，使气泡不重叠吗？

请帮助！我相信这个问题将来会帮助很多初学者，因为在SO或其他平台的任何地方都无法解决。