Reading and writing data

A short description of the post.

1. Load the R packages 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 to ‘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-data",
              "co-emissions-per-capita.csv")

emissions <- read_csv(file_csv)

4. Show the 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==1994’ THEN use ‘skim’ to calculate the descriptive statistics

tidy_emissions %>% 
  filter(year==1994) %>% 
  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	1994.00	0.00	1994.00	1994.00	1994.00	1994.00	1994.00	▁▁▇▁▁
annual_co2_emissions_per_capita	0	1	4.99	6.92	0.02	0.57	2.73	7.36	59.77	▇▁▁▁▁

7. 12 observations have a missing code. How are these observations different? start with ‘tidy_emissions’ then extract rows with ‘year==1994’ and are missing a code

tidy_emissions %>% 
  filter(year==1994,is.na(code))

# A tibble: 12 x 4
   entity                     code   year annual_co2_emissions_per_ca~
   <chr>                      <chr> <dbl>                        <dbl>
 1 Africa                     <NA>   1994                         1.03
 2 Asia                       <NA>   1994                         2.31
 3 Asia (excl. China & India) <NA>   1994                         3.25
 4 EU-27                      <NA>   1994                         8.46
 5 EU-28                      <NA>   1994                         8.63
 6 Europe                     <NA>   1994                         8.85
 7 Europe (excl. EU-27)       <NA>   1994                         9.36
 8 Europe (excl. EU-28)       <NA>   1994                         9.22
 9 North America              <NA>   1994                        14.1 
10 North America (excl. USA)  <NA>   1994                         5.07
11 Oceania                    <NA>   1994                        11.7 
12 South America              <NA>   1994                         2.11

Entities that are not countries do not have country codes.

8. Start with tidy_emissions THEN

use ‘filter to extract rows with year==1994 and without misiing codes THEN use ’select’ to drop the ‘year’ variable THEN use ‘rename’ to change the variable ‘entity’ to ‘country’ assign the output to ‘emissions_1994’

emissions_1994 <- tidy_emissions %>% 
  filter(year==1994,!is.na(code)) %>% 
  select(-year) %>% 
  rename(country=entity)

9. Which 15 countries have the highest ‘annual_co2_emissions_per_capita’?

start with ‘emissions_1994’ 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_1994 %>% 
  slice_max(annual_co2_emissions_per_capita,n=15)

10. Which 15 countries have the lowest ‘annual_co2_emissions_per_capita’?

start with ‘emissions_1994’ THEN use ‘slice_min’ to extract the 15 rows withe lowest values assign the output to ‘min_15_emitters’

min_15_emitters <- emissions_1994 %>% 
  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 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_1994’ 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 1994",
       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-data"))

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

preview: preview.png