R语言get_map报错及ggmap轴刻度重复问题技术求助

Hey there! Let's break down what's happening here and how to get rid of that warning.

Why the Warning Shows Up #

When you call ggmap(map), the function automatically generates x and y axis scales tailored to the map you've loaded. When you add scale_x_continuous() and scale_y_continuous() afterward, R is letting you know it's replacing those auto-generated scales with your custom ones. This warning doesn't actually break your code—your map will still render with the limits you set—but it's a sign that there's a cleaner way to get the result you want.

Solution 1: Set Limits Directly in ggmap() #

You can skip adding separate scale layers entirely by specifying your coordinate limits when you first call ggmap(), using the xlim, ylim, and extent parameters. This matches your original goal of removing extra whitespace and avoids the warning:

tschamut <- ggmap(map, 
                  extent = "device",
                  xlim = c(-13.4003, -13.39943), 
                  ylim = c(35.419, 35.41961))

The extent = "device" argument ensures the map fills exactly the coordinate range you set, just like expand = c(0,0) did in your original code.

Solution 2: Use coord_cartesian() Instead of Scale Layers #

If you prefer to add the range restriction after loading the map, use coord_cartesian() instead of replacing the scales. This function zooms the map to your desired area without altering the underlying axis scales, so no warning is triggered:

tschamut <- ggmap(map) +
  coord_cartesian(xlim = c(-13.4003, -13.39943), 
                  ylim = c(35.419, 35.41961),
                  expand = FALSE)

expand = FALSE here removes the small padding around your coordinate limits, just like your original expand = c(0,0).

Either approach will give you the cropped map you need without the annoying warning. Pick whichever fits better with your code workflow!

内容的提问来源于stack exchange，提问作者user1607