ggplot图形保存为PDF时格式异常：每页图形数量与大小不符

Got it, let's tackle this issue where your PDF is only showing one plot per page (taking up half/third the space) instead of the number you specified with nrow. Here's what's likely going wrong and how to fix it:

First: Make Sure You're Combining Plots Correctly #

The most common mistake here is trying to print plots individually instead of merging them into a single grid. If you just call print(p1) then print(p2) in your script, R will save each as a separate page—even if you set nrow somewhere else. You need to combine your plots into one object first.

Option 1: Use patchwork (Modern & Intuitive)

patchwork is the go-to package for combining ggplot2 plots these days. It's flexible and easy to use:

# Load required packages
library(ggplot2)
library(patchwork)

# Create your individual plots (replace with your actual plots from the dput data)
p1 <- ggplot(your_data, aes(x = var1, y = var2)) + geom_line() + ggtitle("Plot 1")
p2 <- ggplot(your_data, aes(x = var3, y = var4)) + geom_bar() + ggtitle("Plot 2")
p3 <- ggplot(your_data, aes(x = var5, y = var6)) + geom_point() + ggtitle("Plot 3")

# Combine plots with your desired rows/columns
# For 2 plots per page:
combined_2pp <- wrap_plots(p1, p2, p3, nrow = 2)  # First page has 2 plots, second has 1
# For 3 plots per page:
combined_3pp <- wrap_plots(p1, p2, p3, nrow = 3)

# Save to PDF with adjusted dimensions
ggsave(
  "multi_plot.pdf",
  plot = combined_2pp,  # Swap with combined_3pp if needed
  width = 8,            # Adjust based on your plot needs (inches)
  height = 10,          # Taller height for multiple rows
  units = "in",
  dpi = 300,
  device = cairo_pdf    # Optional: Fixes some rendering quirks
)

Option 2: Use gridExtra (Legacy but Reliable)

If you prefer the older gridExtra package, this works too:

library(gridExtra)

# Combine plots
grid_2pp <- grid.arrange(p1, p2, nrow = 2)
grid_3pp <- grid.arrange(p1, p2, p3, nrow = 3)

# Save
ggsave("grid_multi_plot.pdf", grid_2pp, width = 8, height = 10)

Second: Adjust Plot Size & Layout #

If you're still seeing plots take up only part of the page, tweak these settings:

• Adjust ggsave dimensions: If you set nrow=2, make the height of your PDF large enough to fit both plots without compression. For example, height=10 inches works better than height=6 for two stacked plots.
• Set aspect ratio: Force each plot to a consistent size with theme(aspect.ratio = 1) (or another value like 0.75) in your individual ggplot calls. This prevents plots from stretching/squishing unevenly.
• Control row/column heights: In patchwork, use the heights parameter to ensure equal spacing:

  combined_plots <- wrap_plots(p1, p2, nrow = 2, heights = c(1, 1))  # Equal height for both plots
  

• Trim excess margins: Reduce wasted space around plots with theme(plot.margin = margin(5, 5, 5, 5)) (values are top/right/bottom/left in mm).

Third: Verify Your Plot Objects #

Double-check that you're passing the combined plot object to ggsave—not just a single plot. If you accidentally pass p1 instead of combined_2pp, you'll only get that one plot in the PDF.

That should get your plots displaying correctly per page, with the size you want!

内容的提问来源于stack exchange，提问作者user113156