Reading and Writing Data

Practice reading and writing data, more dplyr and a plot.

1. Load the r packages that we will use.

library(tidyverse)
library(here)
library(janitor)
library(skimr)

2. Download \(CO_2\) emissions per capita from Our World in Data into the directory of this post.

3. Assign the location of the file to the file_csv. The data should be in the same directory as this file.

• Read the data into R and assign it to emissions.

file_csv  <- here("_posts",
                  "2022-02-22-reading-and-writing",
                  "co-emissions-per-capita.csv")

emissions  <- read_csv(file_csv)

4. Show the first 10 rows (observations of) emissions

emissions  

# A tibble: 23,307 × 4
   Entity      Code   Year `Annual CO2 emissions (per capita)`
   <chr>       <chr> <dbl>                               <dbl>
 1 Afghanistan AFG    1949                              0.0019
 2 Afghanistan AFG    1950                              0.0109
 3 Afghanistan AFG    1951                              0.0117
 4 Afghanistan AFG    1952                              0.0115
 5 Afghanistan AFG    1953                              0.0132
 6 Afghanistan AFG    1954                              0.013 
 7 Afghanistan AFG    1955                              0.0186
 8 Afghanistan AFG    1956                              0.0218
 9 Afghanistan AFG    1957                              0.0343
10 Afghanistan AFG    1958                              0.038 
# … with 23,297 more rows

5. Start with emissions data THEN

• use clean_names from the janitor package to make the names easier to work with
• assign the output to tidy_emissions
• show the first 10 rows of tidy_emissions

tidy_emissions   <- emissions %>%
  clean_names()

tidy_emissions

# A tibble: 23,307 × 4
   entity      code   year annual_co2_emissions_per_capita
   <chr>       <chr> <dbl>                           <dbl>
 1 Afghanistan AFG    1949                          0.0019
 2 Afghanistan AFG    1950                          0.0109
 3 Afghanistan AFG    1951                          0.0117
 4 Afghanistan AFG    1952                          0.0115
 5 Afghanistan AFG    1953                          0.0132
 6 Afghanistan AFG    1954                          0.013 
 7 Afghanistan AFG    1955                          0.0186
 8 Afghanistan AFG    1956                          0.0218
 9 Afghanistan AFG    1957                          0.0343
10 Afghanistan AFG    1958                          0.038 
# … with 23,297 more rows

6. Start with the tidy_emissions THEN
   

• use filter to extract rows with year == 1999 THEN
• use skim to calculate the descriptive statistics

tidy_emissions  %>%
  filter(year == 1999)  %>%
  skim()

Table 1: Data summary

Name	Piped data
Number of rows	228
Number of columns	4
_______________________
Column type frequency:
character	2
numeric	2
________________________
Group variables	None

Variable type: character

skim_variable	n_missing	complete_rate	min	max	empty	n_unique	whitespace
entity	0	1.00	4	32	0	228	0
code	12	0.95	3	8	0	216	0

Variable type: numeric

skim_variable	n_missing	complete_rate	mean	sd	p0	p25	p50	p75	p100	hist
year	0	1	1999.00	0.00	1999.00	1999.00	1999.00	1999.0	1999.00	▁▁▇▁▁
annual_co2_emissions_per_capita	0	1	4.75	6.01	0.03	0.71	2.83	7.5	53.91	▇▁▁▁▁

7. 12 observations have a missing code. How are these observations different?

• start with tidy_emissions then extract rows with year == 1999 and are missing a code

tidy_emissions  %>% 
  filter(year == 1999, is.na(code))  

# A tibble: 12 × 4
   entity                     code   year annual_co2_emissions_per_ca…
   <chr>                      <chr> <dbl>                        <dbl>
 1 Africa                     <NA>   1999                         1.05
 2 Asia                       <NA>   1999                         2.35
 3 Asia (excl. China & India) <NA>   1999                         3.19
 4 EU-27                      <NA>   1999                         8.42
 5 EU-28                      <NA>   1999                         8.56
 6 Europe                     <NA>   1999                         8.46
 7 Europe (excl. EU-27)       <NA>   1999                         8.48
 8 Europe (excl. EU-28)       <NA>   1999                         8.22
 9 North America              <NA>   1999                        14.4 
10 North America (excl. USA)  <NA>   1999                         5.35
11 Oceania                    <NA>   1999                        12.6 
12 South America              <NA>   1999                         2.45

Entities that are not countries do not have country codes.

8. Start with tidy_emissions THEN

• use filter to extract rows with year == 1999 and without missing codes THEN
• use select to drop the year variable THEN
• use rename to change the variable entitity to country
• assign the output to emissions_1999

emissions_1999  <- tidy_emissions  %>%
  filter(year == 1999, !is.na(code))   %>%
  select(-year)  %>%
  rename(country = entity)

9. Which 15 countries have the highest annual_co2_emissions_per_capita?

• start with emissions_1999 THEN
• use slice_max to extract the 15 rows with the annual_co2_emissions_per_capita
• assign the output to max_15_emitters

max_15_emitters  <- emissions_1999 %>%
  slice_max(annual_co2_emissions_per_capita, n =15)

10. Which 15 countries have the lowest annual_co2_emissions_per_capita?

• start with emissions_1999 THEN
• use slice_min to extract the 15 rows with the lowest values
• assign the output to min_15_emitters

min_15_emitters  <- emissions_1999  %>%
  slice_min(annual_co2_emissions_per_capita, n = 15)

11. Use bind_rows to bind together the max_15_emitters and min_15_emitters

• assign the output to max_min_15

max_min_15  <- bind_rows(max_15_emitters, min_15_emitters)

12. Export max_min_15 to 3 file formats

max_min_15  %>% write_csv("max_min_15.csv") # comma-separated values
max_min_15  %>% write_tsv("max_min_15.tsv")  # tab separated
max_min_15  %>% write_delim("max_min_15.psv", delim = "|") # pipe-separated

13. Read the 3 file formats into R

max_min_15_csv <-  read_csv("max_min_15.csv") # comma-separated values
max_min_15_tsv <-  read_tsv("max_min_15.tsv")  # tab separated
max_min_15_psv <-  read_delim("max_min_15.psv", delim = "|") # pipe-separated

14. Use setdiff to check for any differences among max_min_15_csv, max_min_15_tsv and max_min_15_psv

setdiff(max_min_15_csv, max_min_15_tsv)

# A tibble: 0 × 3
# … with 3 variables: country <chr>, code <chr>,
#   annual_co2_emissions_per_capita <dbl>

Are there any differences?

15. Reorder country in max_min_15 for plotting and assign to max_min_15_plot_data

• start with start with emissions_1999 THEN
• use mutate to reorder country according to annual_co2_emissions_per_capita

max_min_15_plot_data  <- max_min_15 %>%
  mutate(country = reorder(country, annual_co2_emissions_per_capita))  

16. Plot max_min_15_plot_data

ggplot(data = max_min_15_plot_data, 
       mapping = aes(x= annual_co2_emissions_per_capita, y = country)) +
  geom_col() +
  labs(title = "The top 15 and bottom 15 per capita CO2 emissions",
       subtitle = "for 1999", 
       x = NULL, 
       y = NULL)  

17. Save the plot directory with this post

ggsave(filename = "preview.png", 
       path = here("_posts", "2022-02-22-reading-and-writing"))

18. Add preview.png to yaml chuck at the top of this file

preview: preview.png