如何在多个多面 ggplot2 图形中实现相同的面大小和比例? [英] How achieve identical facet sizes and scales in several multi-facet ggplot2 graphics?

问题描述

我有一系列 ggplot2 图形，它们的水平面数量恒定但垂直面数量不同.我想以横向 a4 格式将图形保存为 .pdf.

I have a series of ggplot2 graphics with a constant number of horizontal but differing number of vertical facets. I would like to save the graphics as .pdf on landscape a4 format.

但是，我不知道如何实现相同比例的刻面.如果我尝试手动调整它并针对不同数量的垂直面改变 width 和 height，则图之间的比例会有所不同，即，我得到不同的点大小和线宽.

However, I don't know how I can achieve identical proportions of the facets. If I try to tweak it manually and vary width and height for different numbers of vertical facets, the scales vary between plots, i.e., I get different points sizes and line widths.

本质上，对于具有可变数量(垂直)面的图，我如何才能实现相同的面大小和比例?

In essence, how can I achieve identical facets sizes and scales for plots with a variable number of (vertical) facets?

这是一个例子:

df <- expand.grid(a = 1:2, b = 1:5, x = 1:10)
df$y <- df$x
plot <- ggplot(data = df, mapping = aes(x = x, y = y)) +
            geom_point()
plot1 <- plot + facet_grid(facets = "a ~ b")
plot2 <- plot + facet_grid(facets = ". ~ b")

ggsave(filename = "./figures/plot1.pdf", plot = plot1,
   height = 210, width = 297, units = "mm")

ggsave(filename = "./figures/plot2.pdf", plot = plot2,
   height = 210, width = 297, units = "mm")

推荐答案

我使用这段代码将面板大小设置为绝对值，也许对这里有帮助

I use this code to set panel sizes to absolute values, maybe it helps here

set_panel_size <- function(p=NULL, g=ggplotGrob(p), file=NULL, 
                           margin = unit(1,"mm"),
                           width=unit(4, "cm"), 
                           height=unit(4, "cm")){

  panels <- grep("panel", g$layout$name)
  panel_index_w<- unique(g$layout$l[panels])
  panel_index_h<- unique(g$layout$t[panels])
  nw <- length(panel_index_w)
  nh <- length(panel_index_h)

if(getRversion() < "3.3.0"){

   # the following conversion is necessary
   # because there is no `[<-`.unit method
   # so promoting to unit.list allows standard list indexing
   g$widths <- grid:::unit.list(g$widths)
   g$heights <- grid:::unit.list(g$heights)

   g$widths[panel_index_w] <-  rep(list(width),  nw)
   g$heights[panel_index_h] <- rep(list(height), nh)

} else {

   g$widths[panel_index_w] <-  rep(width,  nw)
   g$heights[panel_index_h] <- rep(height, nh)

}

  if(!is.null(file))
    ggsave(file, g, 
           width = convertWidth(sum(g$widths) + margin, 
                                unitTo = "in", valueOnly = TRUE),
           height = convertHeight(sum(g$heights) + margin,  
                                  unitTo = "in", valueOnly = TRUE))

  invisible(g)
}

print.fixed <- function(x) grid.draw(x)

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