在ggplot2中手动设置填充刻度：俄亥俄州地图分区间着色需求

Got it, let's get your color binning working! The problem with scale_fill_continuous is that it creates a smooth gradient for continuous values, but you need distinct colors for specific value ranges. Here's how to adjust your code to match your desired color scheme:

Step 1: Add a Binned Variable to Your Data #

First, we'll convert your continuous wheat_pmt variable into a discrete factor with your specified intervals. Use the cut() function to define these bins:

# Create a new binned variable for payment ranges
oh_map$payment_bin <- cut(
  oh_map$wheat_pmt,
  breaks = c(0, 10, 20, 30, 34), # Matches your limit of 0-34
  labels = c("0-10", "11-20", "21-30", "31-34"),
  include.lowest = TRUE # Ensures the lowest value (0) is included in the first bin
)

The include.lowest = TRUE parameter makes sure values exactly equal to the first break (0) are captured in the "0-10" bin (since cut() defaults to left-exclusive, right-inclusive intervals).

Step 2: Update Your ggplot Code #

Modify the fill aesthetic to use the new payment_bin variable, and replace scale_fill_continuous with scale_fill_manual to assign your custom colors:

ggplot(oh_map, aes(x = long, y = lat)) +
  geom_polygon(aes(fill = payment_bin, group = group)) +
  geom_path(aes(group = group)) +
  geom_text(data = cnames, aes(label = paste0("$", round(wheat_pmt, digits = 0)), 
                               family="A", fontface="bold", size=4.2)) +
  # Custom color mapping for each bin
  scale_fill_manual(
    values = c(
      "0-10" = "green",
      "11-20" = "blue",
      "21-30" = "orange",
      "31-34" = "red" # Adjust this if you want a different color for the top bin
    ),
    na.value = "black",
    name = "Dollars per Acre" # Updates legend title to match your original
  ) +
  labs(
    title = "Ohio Wheat ARC-CO Payments: Program Year 2018",
    subtitle = "Rounded to Nearest Dollar, adjusted for 85% of Base Acres and a 6.8% Government Sequestration",
    caption = "Data Source: Author Calculation"
  ) +
  theme(
    axis.line=element_blank(), 
    axis.text.x=element_blank(), 
    axis.text.y=element_blank(), 
    axis.ticks=element_blank(), 
    axis.title.x=element_blank(), 
    axis.title.y=element_blank(), 
    panel.grid.major = element_blank(), 
    panel.grid.minor = element_blank(), 
    panel.border = element_blank(), 
    panel.background = element_blank(), 
    legend.position = "", # Keeps your original legend hidden; change to "right" if needed
    plot.title = element_text(hjust = 0.5, family="A", face="bold", size = 20.0), 
    plot.subtitle = element_text(hjust = 0.5, family="A", face="bold")
  )

Key Notes: #

• If you need to adjust the intervals (e.g., add a 35+ bin), just update the breaks and labels in the cut() function, then add a corresponding color to scale_fill_manual.
• The legend.position = "" keeps your legend hidden as in your original code. If you want to display the bin legend, change this to "right", "bottom", or another valid position.

内容的提问来源于stack exchange，提问作者Ben Brown