RMarkdown：使用循环在同一块中创建多个GGPlot

我试图在RMarkdown文档的单个块中使用for循环生成多个绘图（在ggplot2中）

当我硬编码代码以生成两个绘图时，绘图将按预期呈现。请参阅我的代码中标题为“硬编码方法”的部分

但是，当我将两个图的参数加载到一个列表中并在列表中循环时，这些图不会显示出来。我也没有看到任何错误。请参阅我代码中标题为“循环方法”的部分

谁能告诉我发生了什么事，我怎样才能解决它？谢谢

• 卡提克

这是我的密码：

---
title: "Test for multiple plots"
author: "KC"
date: "4/3/2020"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

# Hardcoded Method

Sample Plot - One plot at a time 

```{r Multiple Plots separately listed, echo=TRUE, fig.keep="all"}
library(ggplot2)
library(datasets)

combo = c("temperature", "pressure")
ggplot(pressure, 
       mapping=aes(x=base::get(combo[1]), y=base::get(combo[2]))) + 
  geom_point() + 
  labs(x=combo[1], 
       y=combo[2], 
       title=paste("Hardcoded Method:", paste(combo, collapse=" vs ")))

combo = c("pressure", "temperature")
ggplot(pressure, 
       mapping=aes(x=base::get(combo[1]), y=base::get(combo[2]))) + 
  geom_point() + 
  labs(x=combo[1], 
       y=combo[2], 
       title=paste("Hardcoded Method:", paste(combo, collapse=" vs ")))

```

# Loop Method

Now, I use a loop method to generate the same plots.  

```{r Multiple Plots in a loop, echo=TRUE, fig.keep="all"}
library(ggplot2)
library(datasets)
combos = list(c("temperature", "pressure"), c("pressure", "temperature"))

for (combo in combos) {
  # combo = combos[[1]]
  print(paste("Plotting", paste(combo, collapse=" vs ")))
  ggplot(pressure, 
         mapping=aes(x=base::get(combo[1]), y=base::get(combo[2]))) + 
    geom_point() + 
    labs(x=combo[1], 
         y=combo[2], 
         title=paste("Loop Method:", paste(combo, collapse=" vs ")))
}

```

---

在带有标记文件的代码块中使用

for

循环时，需要显式地

打印（）。因此，以下代码不起作用：

for (i in length(x)) {
    ggplot(...)
}

您需要转换为以下内容：

for (i in length(x)) {
    p <- ggplot(...)
    print(p)
}

for（长度为i（x））{
P