Reading and Writing data

Practice reading and writing data, more dplyr and a plot

1. Load the 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 for this post.

3. Assign the location of the file 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", 
                 "2022-02-19-reading-and-writing-data",   "co-emissions-per-capita.csv")

emissions <- read_csv(file_csv)

4. Show first 10 rows (observations of) emissions

emissions

# A tibble: 23,307 x 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 x 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 == 2004
• use skim to calculate the descriptive statistics

tidy_emissions %>% 
  filter(year == 2004) %>% 
  skim()

Table 1: Data summary

Name	Piped data
Number of rows	229
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	229	0
code	12	0.95	3	8	0	217	0

Variable type: numeric

skim_variable	n_missing	complete_rate	mean	sd	p0	p25	p50	p75	p100	hist
year	0	1	2004.00	0.00	2004.00	2004.00	2004.00	2004.00	2004.0	▁▁▇▁▁
annual_co2_emissions_per_capita	0	1	5.43	6.99	0.02	0.83	3.23	8.45	56.7	▇▁▁▁▁

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

• Start with tidy_emissions then,
• extract rows with year == 2004 and are missing a code.

tidy_emissions %>% 
  filter(year == 2004, is.na(code))

# A tibble: 12 x 4
   entity                     code   year annual_co2_emissions_per_ca~
   <chr>                      <chr> <dbl>                        <dbl>
 1 Africa                     <NA>   2004                         1.16
 2 Asia                       <NA>   2004                         2.97
 3 Asia (excl. China & India) <NA>   2004                         3.61
 4 EU-27                      <NA>   2004                         8.68
 5 EU-28                      <NA>   2004                         8.79
 6 Europe                     <NA>   2004                         8.81
 7 Europe (excl. EU-27)       <NA>   2004                         8.96
 8 Europe (excl. EU-28)       <NA>   2004                         8.80
 9 North America              <NA>   2004                        14.5 
10 North America (excl. USA)  <NA>   2004                         5.53
11 Oceania                    <NA>   2004                        13.2 
12 South America              <NA>   2004                         2.36

• Entities that are not countries do not have country codes.

8. Start with tidy_emissions THEN

• use filter to extract rows with year == 2004 and
• without missing codes THEN,
• use select to drop the year variable THEN,
• use the rename to change the variable entity to country.

emissions_2004 <- tidy_emissions %>% 
  filter(year == 2004, !is.na(code)) %>% 
  select(-year) %>% 
  rename(country = entity)

emissions_2004

# A tibble: 217 x 3
   country             code  annual_co2_emissions_per_capita
   <chr>               <chr>                           <dbl>
 1 Afghanistan         AFG                             0.036
 2 Albania             ALB                             1.32 
 3 Algeria             DZA                             2.69 
 4 Andorra             AND                             7.35 
 5 Angola              AGO                             0.997
 6 Anguilla            AIA                             9.89 
 7 Antigua and Barbuda ATG                             4.56 
 8 Argentina           ARG                             4.08 
 9 Armenia             ARM                             1.23 
10 Aruba               ABW                            26.5  
# ... with 207 more rows

9. Which 15 countries have the highest annual_co2_emissions_per_capita?

• start with emissions_2004 THEN,
• use slice_max to extract the 15 rows with annual_co2_emissions_per_capita,
• assign the output to max_15_emitters

max_15_emitters <- emissions_2004 %>% 
  slice_max(annual_co2_emissions_per_capita, n = 15)

10. Which 15 countries have the lowest annual_co2_emissions_per_capita?

• start with emissions_2004 THEN,
• use slice_min to extract the 15 rows with the lowest values
• assign the output to min_15_emitters.

min_15_emitters <- emissions_2004 %>% 
  slice_min(annual_co2_emissions_per_capita, n =15)

11. Use bind_rows to bind together the max_15_emitter and min_15_emitters assign the outpout to max_min_15.

max_min_15 <- bind_rows(max_15_emitters, min_15_emitters)

12. Export max_min_15 to 3 files 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 value
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_psv)

# A tibble: 0 x 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 emissions_2004 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 2004",
       x = NULL,
       y = NULL)

17. Save the plot directory with this post

ggsave(filename = "preview.png", path = here("_posts", "2022-02-19-reading-and-writing-data"))

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

preview: preview.png