如何使用 R Tidyverse 从 PDF 表中读取表头？

Question

我想使用 R 和 Tidyverse 编写一个（长）语句来从 PDF 表中读取数据并显示为动画图。

我不能正确的是

1. 检索表头
2. 并将数值转换为数字格式。

请注意，我尝试这个是因为我想学习使用 Tidyverse 函数。通过多个步骤，我确实成功了（请参见下面的代码）。

我只是想了解它是否可能在一个连续的“流程”中。

感谢您的建议！

#
# Read data from table in PDF and show as animated plot.
# BvH. 2019-04-05
#

library(tidyverse)  # i like to use the tidyverse
library(tabulizer)  # needed to read tables from pdf-documents
library(gganimate)  # animated plots based on ggplot2
library(gifski)     # fastest renderer...

###############################################################################
# load the data (source:The Brewers of Europe) and extract table from pdf
beer_production_2010_2016.df <- 
  tabulizer::extract_tables(file = "https://brewersofeurope.org/uploads/mycms-files/documents/publications/2017/Statistics-201712-001.pdf", 
                            pages = 9,
                            area = list(c(65, 55, 530, 550))) %>%
  as.data.frame(stringsAsFactors = FALSE)

# set column-names: CAN THIS BE SIMPLIFIED WITH TIDYVERSE FUNCTIONS ?
col_names <- c("Country", "2010", "2011", "2012", "2013", "2014", "2015", "2016")
colnames(beer_production_2010_2016.df) <- col_names

# extract countries
Country <-
  beer_production_2010_2016.df %>%
  slice(2:29) %>% 
  dplyr::pull(Country)

animated.plot.beer_production_2010_2016 <-
  # remove first row and data from non-EU contries and totals 
  beer_production_2010_2016.df %>%
  slice(2:29) %>%
  # remove the country column (contains alphabetical characters): CAN THIS BE SIMPLIFIED ?
  dplyr::select(-Country) %>%
  # remove all decimal grouping symbol's and transform country totals to numeric values
  purrr::map_df(str_replace, pattern = ",", replacement = "") %>% 
  purrr::map_df(as.numeric) %>%
  # add the country column again (as first column)
  tibble::add_column(Country = as.factor(Country), .before = 1) %>%
  # convert from wide to long
  tidyr::gather(key = "year", value = "production", "2010":"2016") %>%
  # keep the top 15 countries for each year. Add utility-columns with display labels for the plot.
  group_by(year) %>%
  mutate(rank = rank(-production),
         Value_rel = production / production[rank == 1],
         Value_lbl = paste0(" ", round(production, digits = 1),  " x 1000 hl")) %>%
  group_by(Country) %>% 
  filter(rank <= 15) %>%
  ungroup() %>%
  # create the plot
  ggplot(aes(x = rank, 
             group = Country,
             fill = Country, 
             color = Country)) +
  geom_tile(aes(y = production / 2,
                height = production,
                width = 0.9), alpha = 0.8, color = NA) +
  geom_text(aes(y = 0, label = paste(Country, " ")), vjust = 0.2, hjust = 1) +
  geom_text(aes(y = production, label = Value_lbl, hjust = 0)) +
  coord_flip(clip = "off", expand = FALSE) +
  scale_x_reverse() +
  guides(color = FALSE, fill = FALSE) +
  theme_void() + 
  theme(legend.position = "none",
        panel.grid.major.x = element_line( size = .1, color = "grey" ),
        panel.grid.minor.x = element_line( size = .1, color = "grey" ),
        plot.title = element_text(size = 25, hjust = 0.5, face = "bold", vjust = -1),
        plot.subtitle = element_text(size = 18, hjust = 0.5, face = "italic"),
        plot.margin = margin(2,2, 2, 4, "cm")) + 
  # animate the plot (with dynamic title that includes the year)
  gganimate::transition_states(year, transition_length = 4, state_length = 1) +
  gganimate::view_follow(fixed_x = TRUE) +
  ggplot2::labs(title = 'European beer production per year : {closest_state}',  
                subtitle = "Top 15 Countries",
                caption = "Data Source: The Brewers of Europe")

# Render into an animated gif
anim.gif <-
  gganimate::animate(animated.plot.beer_production_2010_2016, 
                     nframes = 200, 
                     fps = 20,  
                     width = 1200, 
                     height = 1000, 
                     renderer = gifski_renderer("eu_bier_productie_animatie.gif")) 

Answer 1

老实说，我相信在使用 tidyverse 时，很多事情都是个人喜好问题，当然有最佳实践和预期目的，但开发人员的偏好起着重要作用。

例如，我会改变的主要内容，不是因为它们更好，而是因为这样我更舒服：

col_names <- c("Country", "2010", "2011", "2012", "2013", "2014", "2015", "2016")

to_numeric <- function(x){as.numeric(str_replace(x, pattern = ",", replacement = ""))}
not_factor <- function(x){!is.factor(x)}

animated.plot.beer_production_2010_2016 <-
  # remove first row and data from non-EU contries and totals 
  beer_production_2010_2016.df %>% 
  #~~~~~~~~~ here are the stuff I changed ~~~~~~~~~
  # give the columns the names you want
  `names<-`(col_names) %>% 
  slice(2:29) %>% 
  # set country as factor
  dplyr::mutate(Country = as.factor(Country)) %>% 
  # change the rest to numerics
  dplyr::mutate_if(not_factor, to_numeric) %>% 
  #~~~~~~~~~~~~~~~~~~~~~ end ~~~~~~~~~~~~~~~~~~~~~~~
  # convert from wide to long
  tidyr::gather(key = "year", value = "production", "2010":"2016") %>%
  # keep the top 15 countries for each year. Add utility-columns with display labels for the plot.
  group_by(year) %>%
  mutate(rank = rank(-production),
         Value_rel = production / production[rank == 1],
         Value_lbl = paste0(" ", round(production, digits = 1),  " x 1000 hl")) %>%
 # group_by(Country) %>%  # ~~~~~~~~~~~~~~~~~ are you sure this is necessary?
 filter(rank <= 15) %>% 
 # ungroup() %>%          # ~~~~~~~~~~~~~~~~~ are you sure this is necessary?
 # create the plot
  ggplot(aes(x = rank, 
             group = Country,
             fill = Country, 
             color = Country)) +
  geom_tile(aes(y = production / 2,
                height = production,
                width = 0.9), alpha = 0.8, color = NA) +
  geom_text(aes(y = 0, label = paste(Country, " ")), vjust = 0.2, hjust = 1) +
  geom_text(aes(y = production, label = Value_lbl, hjust = 0)) +
  coord_flip(clip = "off", expand = FALSE) +
  scale_x_reverse() +
  guides(color = FALSE, fill = FALSE) +
  theme_void() + 
  theme(legend.position = "none",
        panel.grid.major.x = element_line( size = .1, color = "grey" ),
        panel.grid.minor.x = element_line( size = .1, color = "grey" ),
        plot.title = element_text(size = 25, hjust = 0.5, face = "bold", vjust = -1),
        plot.subtitle = element_text(size = 18, hjust = 0.5, face = "italic"),
        plot.margin = margin(2,2, 2, 4, "cm")) + 
  # animate the plot (with dynamic title that includes the year)
  gganimate::transition_states(year, transition_length = 4, state_length = 1) +
  gganimate::view_follow(fixed_x = TRUE) +
  ggplot2::labs(title = 'European beer production per year : {closest_state}',  
                subtitle = "Top 15 Countries",
                caption = "Data Source: The Brewers of Europe")

请注意，如果您将参数output='data.frame' 传递给函数tabulizer::extract_tables，您将获得第一行作为标题，但您仍需要删除总行数和您不想要的国家/地区