Plot 在 R 中带有 for 循环的多个绘图

Question

I am trying to plot some line graphs from a dataset but with varied y-axis values that are set in the list var. For some reason, all the plots seem to display an empty plot but when I have the same code without the for loop it seems to work. So my question is can I possibly use a for loop to plot multiple plots at once instead of individually plotting them. Am I missing something while plotting this.

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)
}

This is the outcome I am looking for:

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")

Answer 1

As noted by stefan, ggplot thinks you're trying to plot the character which is why you're getting "CAH" on the y-axis. You can refer to the variable with .data[[v]] .

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)
}

Since I don't have access to your data, here's a reproducible example:

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)
}

You could also use lapply for this by wrapping your plot in a function instead. The function may be useful depending on how often you make these plots or to make it easier to fix and share.

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]]