在 R 中使用 for 循环绘制多个图

Posted 2023-02-14

【中文标题】在 R 中使用 for 循环绘制多个图

【英文标题】：Plot multiple plots with a for loop in R

【发布时间】：2022-01-05 09:46:36

【问题描述】：

我正在尝试从数据集中绘制一些线图，但在列表 var 中设置了不同的 y 轴值。出于某种原因，所有图似乎都显示一个空图，但是当我有相同的代码而没有 for 循环时，它似乎可以工作。所以我的问题是我是否可以使用 for 循环一次绘制多个图，而不是单独绘制它们。我在绘制这个时是否遗漏了什么。

var = list("CAH", 'CTLT',"CI","DVA","HSIC","HOLX","HUM","IDXX","INCY","MRK","REGN","VTRS")
for(v in var)
  p<-closing_price %>%
    mutate(date = as.Date(Date,"%m/%d/%y")) %>%
    ggplot(aes(x = date, y = v, group=1)) +
    geom_line() +
     labs(x = "Date", y = "Stock Price ($)", title = glue("v price over time")) +
     scale_x_date(date_minor_breaks = "2 day")
  print(p)

这是我正在寻找的结果：

closing_price %>%
  mutate(date = as.Date(Date,"%m/%d/%y")) %>%
  select(date,CAH) %>%
  ggplot(aes(x = date, y = CAH, group=1)) +
  geom_line() +
   labs(x = "Date", y = "Stock Price ($)", title = "CAH price over time") +
   scale_x_date(date_minor_breaks = "2 day")

【问题讨论】：

v 是一个字符。这就是为什么你会得到一条水平线。试试y = .data[[v]]。参见例如fishandwhistle.net/slides/rstudioconf2020/#7.

【参考方案1】：

正如 stefan 所指出的，ggplot 认为您正在尝试绘制角色，这就是您在 y 轴上获得“CAH”的原因。您可以使用.data[[v]] 引用变量。

var = list("CAH", 'CTLT',"CI","DVA","HSIC","HOLX","HUM","IDXX","INCY","MRK","REGN","VTRS")
for(v in var)
  p<-closing_price %>%
    mutate(date = as.Date(Date,"%m/%d/%y")) %>%
    ggplot(aes(x = date, y = .data[[v]], group=1)) +
    geom_line() +
     labs(x = "Date", y = "Stock Price ($)", title = glue("v price over time")) +
     scale_x_date(date_minor_breaks = "2 day")
  print(p)

由于我无权访问您的数据，这里有一个可重现的示例：

library(tidyverse)
library(zoo)

closing_price <- 
  tibble(
    dt = as.Date(seq(as.yearmon("2020-01-31"), as.yearmon("2020-12-31"), by = 1 / 12), frac = 1),
    CAH = rnorm(12, mean = 10, sd = 2),
    CTLT = rnorm(12, mean = 50, sd = 5),
    CI = rnorm(12, mean = 25, sd = 2)
  )

vars <- c("CAH", "CTLT","CI")

for(v in vars)
  p <-
    ggplot(data = closing_price, aes(x = dt, y = .data[[v]])) +
    geom_line() +
    labs(x = "Date", y = "Stock Price ($)", title = paste(v, "price over time")) +
    scale_x_date(date_minor_breaks = "2 day")
  print(p)

您也可以使用lapply 来代替将您的情节包装在一个函数中。该功能可能很有用，具体取决于您制作这些图的频率或使其更易于修复和共享。

closing_price_plot <- function(data, var)
  p <- 
    data %>%
    ggplot(aes(x = dt, y = .data[[var]], group=1)) +
    geom_line() +
    labs(x = "Date", y = "Stock Price ($)", title = paste(var, "price over time")) +
    scale_x_date(date_minor_breaks = "2 day")
  return(p)
 

## prints out the plots as in the loop
lapply(vars, FUN = closing_price_plot, data = closing_price)

## save them to a list instead
p <- list()
p <- lapply(vars, FUN = closing_price_plot, data = closing_price)

## view the first plot
p[[1]]