R：将数据帧传递到创建 ggplot2 绘图的函数时出错（data` 必须是 <data.frame>，而不是字符串“df1”）

Question

我需要从几个不同的源数据帧绘制大约 30 个 ggplot2 图，因此我编写了一个函数来创建图，并编写了一个 params 数据帧来存储绘图函数参数。当将参数从 params 数据帧传递到函数时，我收到此错误消息：

data

必须是 ，或者可以被

fortify()

强制转换的对象，而不是字符串“df1”

这是我的代码，我很感激任何建议：

#load libraries
library(tidyverse)
library(ggthemes)

#set up example dataframe:
df1 <- tibble(
  date = seq(ymd('2023-01-01'), ymd('2023-06-30'), by='1 month'),
  A = runif(6, 1, 20),
  B = runif(6, 1, 20),
  C = runif(6, 1, 20)
)

#function to create the plots
gen_plots <- function(df, x, y, title){
  df |> 
    ggplot(
      mapping = aes(x = {{x}}, y = {{y}})
    ) + 
    geom_line() +
    geom_point() +
    #theme_economist() +
    labs(title = {{title}},
         y = "$/MWh",
         x = NULL)
}
  
#test the function--it works:
test_plot <- gen_plots(df1, date, A, "Segment A")

#dataframe with plot parameters (source dataframe, x column, y column, & title):
params <- data.frame(
  df =  c("df1", "df1", "df1"),
  x = c("date", "date", "date"),
  y = c("A", "B", "C"),
  title = c("Segment A", "Segment B", "Segment C")
)

#desired output is a list containing three plots
#this doesn't work

plots <- pmap(params, gen_plots)

Answer 1

library(tidyverse)

# set up example dataframe:
df1 <- tibble(
  date = seq(ymd("2023-01-01"), ymd("2023-06-30"), by = "1 month"),
  A = runif(6, 1, 20),
  B = runif(6, 1, 20),
  C = runif(6, 1, 20)
)

# function to create the plots
gen_plots <- function(df, x, y, title) {
  df |>
    ggplot(
      mapping = aes(x = {{ x }}, y = {{ y }})
    ) +
    geom_line() +
    geom_point() +
    # theme_economist() +
    labs(
      title = {{ title }},
      y = "$/MWh",
      x = NULL
    )
}

# test the function--it works:
gen_plots(df1, "date", "B", "Segment B")
#> Warning in geom_line(): All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.
#> Warning in geom_point(): All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.

# params
list(
  df <- list(df1, df1, df1),
  x <- c("date", "date", "date"),
  y <- c("A", "B", "C"),
  title <- c("Segment A", "Segment B", "Segment C")
)
#> [[1]]
#> [[1]][[1]]
#> # A tibble: 6 × 4
#>   date           A     B     C
#>   <date>     <dbl> <dbl> <dbl>
#> 1 2023-01-01  1.59  1.16 14.1 
#> 2 2023-02-01 16.5   7.81  8.38
#> 3 2023-03-01  8.41 18.3  14.4 
#> 4 2023-04-01 17.8  16.0  14.0 
#> 5 2023-05-01  6.93  9.07  8.08
#> 6 2023-06-01 15.8   4.27  9.87
#> 
#> [[1]][[2]]
#> # A tibble: 6 × 4
#>   date           A     B     C
#>   <date>     <dbl> <dbl> <dbl>
#> 1 2023-01-01  1.59  1.16 14.1 
#> 2 2023-02-01 16.5   7.81  8.38
#> 3 2023-03-01  8.41 18.3  14.4 
#> 4 2023-04-01 17.8  16.0  14.0 
#> 5 2023-05-01  6.93  9.07  8.08
#> 6 2023-06-01 15.8   4.27  9.87
#> 
#> [[1]][[3]]
#> # A tibble: 6 × 4
#>   date           A     B     C
#>   <date>     <dbl> <dbl> <dbl>
#> 1 2023-01-01  1.59  1.16 14.1 
#> 2 2023-02-01 16.5   7.81  8.38
#> 3 2023-03-01  8.41 18.3  14.4 
#> 4 2023-04-01 17.8  16.0  14.0 
#> 5 2023-05-01  6.93  9.07  8.08
#> 6 2023-06-01 15.8   4.27  9.87
#> 
#> 
#> [[2]]
#> [1] "date" "date" "date"
#> 
#> [[3]]
#> [1] "A" "B" "C"
#> 
#> [[4]]
#> [1] "Segment A" "Segment B" "Segment C"

pmap(list(df, x, y, title), gen_plots)
#> [[1]]
#> Warning in geom_line(): All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.
#> All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.

#> 
#> [[2]]
#> Warning in geom_line(): All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.
#> All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.

#> 
#> [[3]]
#> Warning in geom_line(): All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.
#> All aesthetics have length 1, but the data has 6 rows.
#> ℹ Please consider using `annotate()` or provide this layer with data containing
#>   a single row.

^{创建于 2024-05-06，使用 reprex v2.1.0}