Geom_Point在ggmap中尺寸与颜色比例不符问题求助

Hey there, let's break down why your geom_point might not be scaling correctly with your crime data. From what you've shared, here are the most likely culprits and actionable fixes:

Your Provided Code Snippet #

London <- c(lon=-0.1278, lat=51.5074)
London_map <- get_googlemap(center = London, zoom = 10)
plot(London_map)
LondonRob <- read.csv("Rob London.csv")
Areas <- as.character(LondonRob$ï..Borough)
locs_geo <- geocode(Areas...  # Incomplete code here

Common Issues & Solutions #

• Missing explicit aesthetic mapping to crime data
  If you're using ggmap (since you called get_googlemap), you need to explicitly link the size and color parameters in geom_point to your numeric crime variable (e.g., a column like Total_Robberies or Crime_Rate in LondonRob). Without this, geom_point uses fixed default values instead of scaling with your data.

  Example fix:

  # First, merge geocoded coordinates with your crime data
  locs_geo <- geocode(Areas)
  LondonRob <- cbind(LondonRob, locs_geo)
  
  # Use ggmap + ggplot2 layers for proper scaling
  ggmap(London_map) +
    geom_point(data = LondonRob, aes(x = lon, y = lat, size = Total_Robberies, color = Total_Robberies)) +
    scale_size_continuous(range = c(2, 10))  # Adjust range to fit your map's zoom level
    scale_color_viridis_c(option = "plasma")  # Accessible continuous color scale
  

• Mixing base R plot() with ggplot2 geom_point
  Your current code uses base R's plot(London_map), but geom_point is a ggplot2 function. These two systems don't play well together—you need to use ggmap() to render the map, then add ggplot2 layers on top.

• Unmerged geocoded coordinates
  If locs_geo isn't combined with your LondonRob data frame, your crime metrics won't be linked to the correct geographic points. Always merge the geocoded lon/lat values back into your main dataset before plotting.

• Using discrete scales for numeric data
  If your crime variable is numeric, using discrete size/color scales will break the proportional mapping. Stick to scale_size_continuous and scale_color_continuous (or viridis scales) for numeric data.

If you can share the full code (especially the part where you add geom_point) and details about your crime data column, I can help refine this further!

内容的提问来源于stack exchange，提问作者JohnPorter