使用 ggplot2/gridExtra 保持两个图垂直对齐

Question

我试图将多个 ggplot2 图合并到一张图片中，同时保留对每个元素各自高度的控制。 下面的代码运行良好，它生成一个条形图和一个曲线图，它们彼此完美对齐（参见

here）：

library(ggplot2)
library(grid)
library(gridExtra)

# Save plot as PDF (set to NULL initially)
pdf(file = NULL)

# Data frame for the first plot
df_1 <- data.frame(
    data = c(0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.2, 0.2, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.4, 0.2,
             0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.5, 0.1, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.2, 0.2,
             0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.4, 0.2, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.5, 0.1,
             0.5, 0.1, 0.15, 0.5, 0.5, 0.4),
    base = 1:54,
    value = c(0.9557, 0.4407, 0.141, 3.4229, 3.5197, 4.7386, 6.9897, 0.3958, 4.7268, 1.8085,
              10.5312, 5.9011, 7.9393, 5.7363, 13.8539, 11.2096, 14.8407, 11.4008, 0.5412, 10.3042,
              11.3208, 15.6669, 8.2177, 12.6917, 20.7124, 10.9896, 24.7246, 7.0544, 21.0489, 16.4536,
              7.4753, 28.2106, 32.7284, 29.7557, 23.3567, 29.9186, 30.3813, 15.1307, 20.2323, 34.4262,
              20.8036, 18.7994, 41.7036, 26.828, 10.7628, 28.2335, 4.4982, 3.6528, 33.8571, 11.6208,
              43.54, 26.7859, 22.2176, 11.0588)
)

# First plot with ggplot
plot_1 <- ggplot(df_1, aes(x = base, y = data, fill = value)) +
    geom_bar(stat = 'identity', position = position_dodge(width = 0.9)) +
    scale_fill_distiller(palette = 'YlGnBu') +
    theme(
        axis.text.x = element_text(size = 9, angle = 0, vjust = 0.5),
        axis.text.y = element_text(size = 9),
        legend.position = 'right',
        legend.spacing.x = unit(5, 'pt'),
        legend.text = element_text(margin = margin(0, 0, 0, 0, 'pt'), size = 10),
        legend.key = element_rect(fill = NA),
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),plot.margin = margin(0,0,0,0)
    ) +
    guides(
        colour = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5),
        shape = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5),
        fill = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5)
    )+
    xlim(0, 55)


# Data frame for the second plot
df_2 <- data.frame(
    x1 = c(4, 12, 1, 2),
    x2 = c(9, 15, 24, 54),
    y1 = c(0, 0, 0, 0),
    y2 = c(0, 0, 0, 0),
    priority = c('high', 'low', 'mid', 'high')
)

# Second plot with ggplot
plot_2 <- ggplot(df_2) +
    geom_curve(aes(x = x1, xend = x2, y = y1, yend = y2, color = priority),
               curvature = 1, linewidth = 0.5, ncp = 1000) +
    expand_limits(y = -1) +
    coord_fixed(ratio = 22, ylim = c(-1, 0)) +
    scale_colour_brewer(palette = 'YlGnBu') +
    theme(

        legend.position = 'right',
        legend.spacing.x = unit(5, 'pt'),
        legend.text = element_text(margin = margin(0, 0, 0, 0, 'pt'), size = 10),
        legend.key = element_rect(fill = NA),
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),plot.margin = margin(0,0,0,0)
    ) +
    guides(
        colour = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5),
        shape = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5),
        fill = guide_legend(label.position = 'right', title.position = 'top', title.hjust = 0.5)
    ) +
    xlim(0, 55)


# List of ggplot objects
plots <- list(plot_1, plot_2)  # Add as many plots as you need

# Apply a small margin to each plot to reduce extra white space
plots_adjusted <- lapply(plots, "+", theme(plot.margin = margin(0, 0, 0, 0)))

# Convert adjusted plots to gtables
grob_plots <- lapply(plots_adjusted, ggplotGrob)

# Calculate the maximum widths across all plots
max_widths <- do.call(unit.pmax, lapply(grob_plots, function(g) g$widths))

# Set each plot's widths to the calculated maximum widths
grob_plots <- lapply(grob_plots, function(g) { g$widths <- max_widths; g })

# Arrange the grobs with specific heights
combined_plot <- arrangeGrob(grobs = grob_plots, heights = unit(c(1,1), "null"), padding = unit(0, "pt"))


dev.off()

# Save the combined plot to a file
ggsave("~/Downloads/mytest.pdf", combined_plot,dpi = 300)

但是，当我尝试在

ggsave()

 中修改输出 PDF 文件的宽度（例如通过设置 

width=20

）时，绘图的相对比例会丢失，并且只有第一个绘图会扩展以填充打印区域（参见

此处）。

你能告诉我如何解决这个问题吗？

Answer 1

出现您遇到的问题是因为

ggsave()

 独立于 

arrangeGrob()

 中指定的相对布局重新缩放绘图。为了确保在调整输出 PDF 尺寸时保留比例，您需要显式定义组合图的纵横比并统一处理缩放。

library(ggplot2)
library(grid)
library(gridExtra)

# Data frame for the first plot
df_1 <- data.frame(
    data = c(0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.2, 0.2, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.4, 0.2,
             0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.5, 0.1, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.2, 0.2,
             0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.4, 0.2, 0.25, 0.5, 0.1, 0.15, 0.5, 0.5, 0.5, 0.1,
             0.5, 0.1, 0.15, 0.5, 0.5, 0.4),
    base = 1:54,
    value = c(0.9557, 0.4407, 0.141, 3.4229, 3.5197, 4.7386, 6.9897, 0.3958, 4.7268, 1.8085,
              10.5312, 5.9011, 7.9393, 5.7363, 13.8539, 11.2096, 14.8407, 11.4008, 0.5412, 10.3042,
              11.3208, 15.6669, 8.2177, 12.6917, 20.7124, 10.9896, 24.7246, 7.0544, 21.0489, 16.4536,
              7.4753, 28.2106, 32.7284, 29.7557, 23.3567, 29.9186, 30.3813, 15.1307, 20.2323, 34.4262,
              20.8036, 18.7994, 41.7036, 26.828, 10.7628, 28.2335, 4.4982, 3.6528, 33.8571, 11.6208,
              43.54, 26.7859, 22.2176, 11.0588)
)

plot_1 <- ggplot(df_1, aes(x = base, y = data, fill = value)) +
    geom_bar(stat = 'identity', position = position_dodge(width = 0.9)) +
    scale_fill_distiller(palette = 'YlGnBu') +
    theme(
        axis.text.x = element_text(size = 9),
        legend.position = 'right',
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),
        plot.margin = margin(0, 0, 0, 0)
    ) +
    xlim(0, 55)

df_2 <- data.frame(
    x1 = c(4, 12, 1, 2),
    x2 = c(9, 15, 24, 54),
    y1 = c(0, 0, 0, 0),
    y2 = c(0, 0, 0, 0),
    priority = c('high', 'low', 'mid', 'high')
)

plot_2 <- ggplot(df_2) +
    geom_curve(aes(x = x1, xend = x2, y = y1, yend = y2, color = priority),
               curvature = 1, linewidth = 0.5, ncp = 1000) +
    expand_limits(y = -1) +
    coord_fixed(ratio = 22, ylim = c(-1, 0)) +
    scale_colour_brewer(palette = 'YlGnBu') +
    theme(
        legend.position = 'right',
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),
        plot.margin = margin(0, 0, 0, 0)
    ) +
    xlim(0, 55)

# Combine plots
grob_plots <- list(ggplotGrob(plot_1), ggplotGrob(plot_2))

# Equalize widths
max_widths <- do.call(unit.pmax, lapply(grob_plots, function(g) g$widths))
grob_plots <- lapply(grob_plots, function(g) { g$widths <- max_widths; g })

# Combine with height proportions (e.g., 2:1)
combined_plot <- arrangeGrob(
    grobs = grob_plots,
    heights = c(2, 1), # Control relative heights here
    padding = unit(0, "pt")
)

# Save the plot
ggsave(
    "~/Downloads/mytest.pdf",
    plot = combined_plot,
    width = 12, height = 8, dpi = 300
)

希望这有帮助。