ggplot2 中的注释不支持换行符是粘贴和解析的命令

Question

问题

如何进出paste以支持换行符 (\n) parse？annotateggplot2

问题和MWE

我正在尝试使用包中的ggplot2NMDS 分析的应力图进行重现，这是我的 MWE，后面是结果图。metaMDSvegan.

library(ggplot2)
library(tibble)
library(vegan)

set.seed(42) # for reproducibility

data(dune)
fit <- metaMDS(dune)
tib <- tibble(fit$diss, fit$dist, fit$dhat)
colnames(tib) <- c("diss", "dist", "dhat")
stress <- fit$stress
coord_x <- min(tib$diss)
coord_y <- max(tib$dist)
nonmetric_r2 <- round(1 - stress * stress, digits = 3)
linear_r2 <- round(summary(lm(fit$dist~fit$dhat))$adj.r.squared, 3)

## How do I get the newline character to be honored?
nonmetric_label = paste0("Non-metric~fit~italic(R)^2 ==", nonmetric_r2, "~\n Linear~fit~italic(R)^2 ==", linear_r2)

ggplot(tib,
       aes(x = diss, y = dist)) +
  geom_point(color = "blue") +
  geom_line(aes(x = diss, y = dhat), color = "red") +
  annotate(
    geom = "text",
    x = coord_x,
    y = coord_y,
    hjust = 0,
    #vjust = 1,
    label = nonmetric_label, parse = TRUE) +
  labs(x = "Observed Dissimilarity",
       y = "Ordination Distance")

上面的单个注释行应该位于两个单独的行上，如下所示（来自stressplot(fit)）。

违规行是

nonmetric_label = paste0("Non-metric~fit~italic(R)^2 ==", nonmetric_r2, "~\n Linear~fit~italic(R)^2 ==", linear_r2)

如果我在 之前不包含波形符\n，那么换行符之后的所有内容都会消失。我尝试了波浪号放置和放置'\n~Linear~fit'额外的单引号和反引号的各种组合。

如何使所需的注释显示在两行上？

Answer 1

一种方法是使用字符串向量作为标签和坐标向量来匹配所需的注释：

nonmetric_label = c(paste0("Non-metric~fit~italic(R)^2 ==", nonmetric_r2),
                    paste0("Linear~fit~italic(R)^2 ==", linear_r2)) 

ggplot(tib,
       aes(x = diss, y = dist)) +
  geom_point(color = "blue") +
  geom_step(aes(x = diss, y = dhat), color = "red", direction = "vh") +
  annotate(
    geom = "text",
    x = coord_x,
    y = c(coord_y, 0.95*coord_y),
    hjust = 0,
    #vjust = 1,
    label = nonmetric_label, parse = TRUE) +
  labs(x = "Observed Dissimilarity",
       y = "Ordination Distance")

根据 Jari Oksanen 的建议，我已更改geom_line为geom_step. 为了匹配输出，需要stressplot(fit)一个附加参数。direction = "vh"