R语言中无法叠加两层地图的问题求助

Hey there! Let's break down this error and fix your code step by step.

Why the Error Happens #

That plot.new has not been called yet error boils down to a misused parameter in your first plot call:

• The reset = FALSE argument in sf's plot function tells R not to create a new plotting window (it skips running plot.new() under the hood).
• Since this is the first plot in your script, there's no existing plotting window to work with. When you try to add the red Asia layer with add = TRUE, R can't find an open canvas to draw on—hence the error.

How to Fix It #

The simplest fix is to remove reset = FALSE from your first plot. By default, sf's plot function creates a new plotting window when you first use it, which lets you add layers later with add = TRUE:

library(spData)
world_asia = world[world$continent == "Asia", ]
asia = st_union(world_asia)
# First plot creates the window (no need for reset=FALSE)
plot(world["pop"])
# Add the red Asia layer to the existing plot
plot(asia, add = TRUE, col = "red")

If you do need reset = FALSE for a more complex multi-layer workflow, you'll need to manually create a plotting window first and set the correct coordinate limits:

library(spData)
world_asia = world[world$continent == "Asia", ]
asia = st_union(world_asia)

# Manually create a new plotting window
plot.new()
# Set limits to match the world map's bounding box
plot.window(xlim = st_bbox(world)[c(1,3)], ylim = st_bbox(world)[c(2,4)])
# Plot population data without resetting the window
plot(world["pop"], reset = FALSE, add = TRUE)
# Add the red Asia layer
plot(asia, add = TRUE, col = "red")
# Optional: Add axes and a border to clean up the plot
axis(1); axis(2); box()

Quick Tip #

When working with sf objects, using st_geometry() to plot just the spatial shapes can make layer stacking more predictable:

plot(world["pop"])
plot(st_geometry(asia), add = TRUE, col = "red")

内容的提问来源于stack exchange，提问作者Betel