7 Working with single tables in `dplyr`

Data frames are usually the most convenient objects for storing, plotting or analysing data in R. We also need to be able to manipulate data in data frames.

This tutorial will show you how to manipulate data frames using the dplyr package, part of tidyverse.

Everything that can be done with dplyr can be done with base R. The dplyr solution is usually easier to write and understand, and can be faster.

There are many function in dplyr, this tutorial focuses on the functions I find most useful.

7.0.1 Load the package

You can load dplyr with

library("dplyr")

But is is usually more convenient to load tidyverse so that you get ggplot2, dplyr, readr and other useful packages with one command.

library("tidyverse")

7.0.2 More feedback `tidylog`

We can get more feedback on what dplyr functions have done to the data by loading the tidylog package.

library("tidylog")

More than once, tidylog has helped identified bugs in my code.

7.1 The `penguins` dataset

This tutorial will use the penguins dataset from the palmerpenguins package. This dataset includes measurements of three species of penguin.

# Load the data
data("penguins", package = "palmerpenguins")
# Show the data
penguins

## # A tibble: 344 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 341 more rows, and 1 more variable: year <int>

7.2 Selecting columns with `select()`

You can choose which columns of the data frame you want with select().

The first argument is the data, which is supplied by the pipe |>, the next arguments are the names of the columns you want. The names do not need quote marks.

#select species, bill_length_mm & bill_depth_mm
penguins |> 
  select(species, bill_length_mm, bill_depth_mm)

## select: dropped 5 variables (island, flipper_length_mm, body_mass_g, sex, year)

## # A tibble: 344 × 3
##   species bill_length_mm bill_depth_mm
##   <fct>            <dbl>         <dbl>
## 1 Adelie            39.1          18.7
## 2 Adelie            39.5          17.4
## 3 Adelie            40.3          18  
## # … with 341 more rows

This is equivalent to the base R code

#select species, bill_length_mm & bill_depth_mm
penguins[, c("species", "bill_length_mm", "bill_depth_mm")]

## # A tibble: 344 × 3
##   species bill_length_mm bill_depth_mm
##   <fct>            <dbl>         <dbl>
## 1 Adelie            39.1          18.7
## 2 Adelie            39.5          17.4
## 3 Adelie            40.3          18  
## # … with 341 more rows

Remember that if you want to use the output of this code in a further analysis, you need to assign it to an object name with <-.

Exercise

From the penguins data, select

species
species and bill_length_mm
all columns except year

Hint

penguins |> 
  select(___, ___)

7.2.1 `select()` helpers

Sometimes we don’t want to write out the names of all the columns we want to select. We might not even know them all in advance. Fortunately there are some helper functions.

If you want to select() adjacent columns, you can use the notation first:last.

#select species to bill_depth_mm
penguins |> select(species:bill_depth_mm)

## select: dropped 4 variables (flipper_length_mm, body_mass_g, sex, year)

## # A tibble: 344 × 4
##   species island    bill_length_mm bill_depth_mm
##   <fct>   <fct>              <dbl>         <dbl>
## 1 Adelie  Torgersen           39.1          18.7
## 2 Adelie  Torgersen           39.5          17.4
## 3 Adelie  Torgersen           40.3          18  
## # … with 341 more rows

Sometimes it is easier to remove the columns you don’t want. You can do this by putting a - in front of the column name.

#select everything but year and sex
penguins |> select(-year, -sex)

## select: dropped 2 variables (sex, year)

## # A tibble: 344 × 6
##   species island    bill_length_mm bill_depth_mm flipper_length_mm body_mass_g
##   <fct>   <fct>              <dbl>         <dbl>             <int>       <int>
## 1 Adelie  Torgersen           39.1          18.7               181        3750
## 2 Adelie  Torgersen           39.5          17.4               186        3800
## 3 Adelie  Torgersen           40.3          18                 195        3250
## # … with 341 more rows

If there is a pattern to the column names that we want to select (or remove), there are some helper functions. For example, to select columns that start with “bill”, we can use starts_with().

#select bill_length_mm & bill_depth_mm" 
penguins |> select(starts_with("bill"))

## select: dropped 6 variables (species, island, flipper_length_mm, body_mass_g, sex, …)

## # A tibble: 344 × 2
##   bill_length_mm bill_depth_mm
##            <dbl>         <dbl>
## 1           39.1          18.7
## 2           39.5          17.4
## 3           40.3          18  
## # … with 341 more rows

Conversely, if we want to select all columns that end with “mm”, we can use ends_with(). contains() is more flexible and matches() is the most powerful of the helper functions, using regular expressions to identify the columns (see the regular expression tutorial).

Sometimes, you might want to select all the columns of a certain type. For example, to select all the numeric columns we can use the is.numeric function inside select() with the helper where().

penguins |> select(where(is.numeric)) # No brackets on the function

## select: dropped 3 variables (species, island, sex)

## # A tibble: 344 × 5
##   bill_length_mm bill_depth_mm flipper_length_mm body_mass_g  year
##            <dbl>         <dbl>             <int>       <int> <int>
## 1           39.1          18.7               181        3750  2007
## 2           39.5          17.4               186        3800  2007
## 3           40.3          18                 195        3250  2007
## # … with 341 more rows

Other is.* functions exist, for example, is.character for text.

You can also select columns by number (1 being the first column), but this is generally a bad idea because it makes the code difficult to understand and if a new column is added, or the column order is changed, the code will break.

Which of these strategies works best is context dependent.

Exercise

From the penguins data, select

all columns except year
all non-numeric columns
species and columns ending in “mm”

Hint

# hint 1
penguins |> 
  select(-___)

# hint 2
?where

# hint 3
?ends_with

7.3 Renaming columns with `rename`

You can use rename() to rename columns

penguins |> rename(Species = species)

## rename: renamed one variable (Species)

## # A tibble: 344 × 8
##   Species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 341 more rows, and 1 more variable: year <int>

The syntax is new_name = current_name.

You can also rename a column when selecting. This is convenient if you are using select() anyway.

penguins |> select(Species = species)

## select: renamed one variable (Species) and dropped 7 variables

## # A tibble: 344 × 1
##   Species
##   <fct>  
## 1 Adelie 
## 2 Adelie 
## 3 Adelie 
## # … with 341 more rows

7.4 Moving columns with `relocate()`

Sometimes it is useful to reorder the columns. This is never necessary for data analysis or plotting, but can be needed when making a table for presentation.

penguins |> relocate(island)

## relocate: columns reordered (island, species, bill_length_mm, bill_depth_mm, flipper_length_mm, …)

## # A tibble: 344 × 8
##   island species bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>  <fct>            <dbl>         <dbl>            <int>       <int> <fct>
## 1 Torge… Adelie            39.1          18.7              181        3750 male 
## 2 Torge… Adelie            39.5          17.4              186        3800 fema…
## 3 Torge… Adelie            40.3          18                195        3250 fema…
## # … with 341 more rows, and 1 more variable: year <int>

The default is to move the named column first, the .before and .after arguments let you move the column into any position.

7.5 Filtering rows with `filter()`

Filtering rows that meet some condition is a very common task.

For example, to filter rows of penguins that have a bill length greater than 40 mm, we can use

penguins |> filter(bill_length_mm > 40)

## filter: removed 102 rows (30%), 242 rows remaining

## # A tibble: 242 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           40.3          18                195        3250 fema…
## 2 Adelie  Torge…           42            20.2              190        4250 <NA> 
## 3 Adelie  Torge…           41.1          17.6              182        3200 fema…
## # … with 239 more rows, and 1 more variable: year <int>

This will filter out each row where the condition is TRUE.

The base R equivalent of this is

penguins[penguins$bill_length_mm > 40, ]

## # A tibble: 244 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           40.3          18                195        3250 fema…
## 2 <NA>    <NA>             NA            NA                 NA          NA <NA> 
## 3 Adelie  Torge…           42            20.2              190        4250 <NA> 
## # … with 241 more rows, and 1 more variable: year <int>

Generally, filter makes it easier to understand, especially with more complex criteria.

Other tests include

== exactly equals. Often a bad idea to use with numeric data
near safe function for testing equality of numeric data as it has a tolerance for rounding errors.

sqrt(2) ^ 2 == 2 # should be true, but rounding errors

## [1] FALSE

sqrt(2) ^ 2 - 2 # the difference

## [1] 4.440892e-16

near(sqrt(2) ^ 2, 2) # safe alternative

## [1] TRUE

!= not equal to
< less than
<= less than or equal to
> greater than
>= greater than or equal to
is.na() for filtering by missing values.
between() for filtering values with a range
%in% is used when you want to test if a value is in a vector

penguins |> 
  filter(species %in% c("Adelie", "Chinstrap"))

## filter: removed 124 rows (36%), 220 rows remaining

## # A tibble: 220 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 217 more rows, and 1 more variable: year <int>

#equivalent to 
penguins |> 
  filter(species == "Adelie" | species == "Chinstrap") # with many alternatives, this gets long

## filter: removed 124 rows (36%), 220 rows remaining

## # A tibble: 220 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 217 more rows, and 1 more variable: year <int>

7.5.1 Filtering on multiple criteria

If we want to filter on multiple criteria, we need to decide whether we want all criteria to be TRUE (AND in Boolean logic), or for one or more to be TRUE (OR in Boolean logic).

If we want all criteria to be TRUE, we can separate them by a comma (or by an & if you want to be explicit).

penguins |> 
  filter(bill_length_mm > 40, bill_depth_mm > 18)

## filter: removed 263 rows (76%), 81 rows remaining

## # A tibble: 81 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           42            20.2              190        4250 <NA> 
## 2 Adelie  Torge…           42.5          20.7              197        4500 male 
## 3 Adelie  Torge…           46            21.5              194        4200 male 
## # … with 78 more rows, and 1 more variable: year <int>

If we want rows where any of the criteria is TRUE, we can separate them by a |.

penguins |> 
  filter(bill_length_mm > 40 | bill_depth_mm > 18)

## filter: removed 53 rows (15%), 291 rows remaining

## # A tibble: 291 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           40.3          18                195        3250 fema…
## 3 Adelie  Torge…           36.7          19.3              193        3450 fema…
## # … with 288 more rows, and 1 more variable: year <int>

We can negate a criterion by putting ! in front of it. So to filter rows that do not have bills longer than 40 mm we can use

penguins |> filter(!bill_length_mm > 40)

## filter: removed 244 rows (71%), 100 rows remaining

## # A tibble: 100 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           36.7          19.3              193        3450 fema…
## # … with 97 more rows, and 1 more variable: year <int>

Of course, in this example, we could also use <= as the test.

7.5.2 Common errors

The commonest error is to use a single = rather than ==. Only the latter is a test of equality. If you do this, the error message is quite helpful.

penguins |> filter(species = "Chinstrap")

## Error: Problem with `filter()` input `..1`.
## x Input `..1` is named.
## ℹ This usually means that you've used `=` instead of `==`.
## ℹ Did you mean `species == "Chinstrap"`?

Another common error is to forget to quote any strings.

penguins |> filter(species == Chinstrap)

## Error: Problem with `filter()` input `..1`.
## ℹ Input `..1` is `species == Chinstrap`.
## x object 'Chinstrap' not found

Exercise

From the penguins data, filter

Gentoo penguins
Gentoo or Adelie penguins
penguins with a mass greater than or equal to 5000g
penguins with a bill length between 45 and 50 mm
Gentoo penguins not from from Dream Island

Hint

#hint 1
penguins |> filter(___ = ___)

#hint 2
?`%in%`

#hint 3
penguins |> filter(___ >= ___)

#hint 4
?between

#hint 5
?`!`

7.6 Slicing the data with `slice()`

Sometimes it is useful to extract rows by row number.

penguins |> slice(3:7)

## slice: removed 339 rows (99%), 5 rows remaining

## # A tibble: 5 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           40.3          18                195        3250 fema…
## 2 Adelie  Torge…           NA            NA                 NA          NA <NA> 
## 3 Adelie  Torge…           36.7          19.3              193        3450 fema…
## 4 Adelie  Torge…           39.3          20.6              190        3650 male 
## 5 Adelie  Torge…           38.9          17.8              181        3625 fema…
## # … with 1 more variable: year <int>

You can use negative numbers to remove rows. Be careful using slice() as if the data change, different rows may be returned.

7.7 Distinct rows with `distinct()`

If there are duplicates in the data, we can remove these with distinct(). distinct() with no extra arguments will remove duplicate rows.

penguins |> distinct()

## distinct: no rows removed

## # A tibble: 344 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 341 more rows, and 1 more variable: year <int>

If we are only interested in some of the columns, we can supply the names of these columns.

penguins |> distinct(island)

## distinct: removed 341 rows (99%), 3 rows remaining

## # A tibble: 3 × 1
##   island   
##   <fct>    
## 1 Torgersen
## 2 Biscoe   
## 3 Dream

Other columns will be removed unless the argument .keep_all = TRUE is used.

Exercise

From the penguins data, find distinct values of

species
species, island and sex

Hint

penguins |> distinct(___, ___)

7.8 Random rows

Sometimes you want to sample rows at random from a data.frame. This can be done with slice_sample(). This can either sample a constant n rows or constant fraction of the rows depending on whether the n or prop argument is used.

penguins |> slice_sample(n = 10)

## slice_sample: removed 334 rows (97%), 10 rows remaining

## # A tibble: 10 × 8
##    species   island    bill_length_mm bill_depth_mm flipper_length_… body_mass_g
##    <fct>     <fct>              <dbl>         <dbl>            <int>       <int>
##  1 Adelie    Torgersen           38.6          21.2              191        3800
##  2 Gentoo    Biscoe              48.7          15.7              208        5350
##  3 Gentoo    Biscoe              47.8          15                215        5650
##  4 Adelie    Biscoe              35.5          16.2              195        3350
##  5 Adelie    Biscoe              38.1          17                181        3175
##  6 Chinstrap Dream               49            19.6              212        4300
##  7 Adelie    Dream               40.9          18.9              184        3900
##  8 Adelie    Biscoe              37.7          18.7              180        3600
##  9 Adelie    Dream               36            17.9              190        3450
## 10 Adelie    Torgersen           45.8          18.9              197        4150
## # … with 2 more variables: sex <fct>, year <int>

7.9 Mutating and adding columns with `mutate`

The function mutate() can add an new column or replace an existing one.

To make a new column called body_mass_kg we can use

penguins |> 
  mutate(body_mass_kg = body_mass_g / 1000)

## mutate: new variable 'body_mass_kg' (double) with 95 unique values and 1% NA

## # A tibble: 344 × 9
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Torge…           39.1          18.7              181        3750 male 
## 2 Adelie  Torge…           39.5          17.4              186        3800 fema…
## 3 Adelie  Torge…           40.3          18                195        3250 fema…
## # … with 341 more rows, and 2 more variables: year <int>, body_mass_kg <dbl>

There are lots of functions that are useful to use with mutate. Any function that returns either a single value or as many values as are in the data can be used.

mutate() is very useful when cleaning data.

See text manipulation tutorial for cleaning text with the stringr package.
See date and time tutorial for cleaning dates and times with the lubridate package.

Exercise

With the penguins data,

convert flipper length to cm
add a column with the ratio of bill width to length

Hint

# hint 1
penguins |> 
  mutate(___ = ___)

7.10 Summarising data with `summarise()`

summarise() lets us summarise data. We can use it if we want to calculate a summary statistic of the data. Remember to separate arguments with a comma.

penguins |> summarise(
  flipper_len_mean = mean(flipper_length_mm, na.rm = TRUE), 
  flipper_len_sd = sd(flipper_length_mm, na.rm = TRUE)
  )

## summarise: now one row and 2 columns, ungrouped

## # A tibble: 1 × 2
##   flipper_len_mean flipper_len_sd
##              <dbl>          <dbl>
## 1             201.           14.1

Only the columns created in the summarise() and any grouping columns (see below) will be kept.

Exercise

With the penguins data, find

the maximum and minimum bill length

Hint

penguins |> 
  summarise(___ = ___(___))

7.10.1 Summarising multiple columns

Sometimes you want to summarise multiple columns at the same time. This can be done with the across() helper function. across() needs to be told which columns to process and what function or functions to use.

penguins |>
   summarise(across(c(bill_length_mm, bill_depth_mm), .fns = mean, na.rm = TRUE))

## summarise: now one row and 2 columns, ungrouped

## # A tibble: 1 × 2
##   bill_length_mm bill_depth_mm
##            <dbl>         <dbl>
## 1           43.9          17.2

#using a list of functions
penguins |>
  summarise(across(.cols = starts_with("bill"), .fns = list(sd = sd, mean = mean), na.rm = TRUE))

## summarise: now one row and 4 columns, ungrouped

## # A tibble: 1 × 4
##   bill_length_mm_sd bill_length_mm_mean bill_depth_mm_sd bill_depth_mm_mean
##               <dbl>               <dbl>            <dbl>              <dbl>
## 1              5.46                43.9             1.97               17.2

You can also use across() with mutate() to mutate several columns at the same time.

7.11 Grouping data with `group_by`

group_by() changes the way that many of the dplyr functions work. Instead of working on the entire dataset, they now work on each group in the data

To find the mean flipper length for each species, we need to group_by() species and then summarise().

penguins |> 
  group_by(species) |> 
  summarise(mean_flipper_length = mean(flipper_length_mm))

## group_by: one grouping variable (species)

## summarise: now 3 rows and 2 columns, ungrouped

## # A tibble: 3 × 2
##   species   mean_flipper_length
##   <fct>                   <dbl>
## 1 Adelie                    NA 
## 2 Chinstrap                196.
## 3 Gentoo                    NA

Grouped data can be ungrouped with ungroup(). This can help prevent surprises!

Exercise

With the penguins data, find

the maximum and minimum bill depth of each species

Hint

penguins |> 
  group_by(___)
  summarise(___ =  ___(___))

7.12 Sorting with `arrange()`

To sort the data frame by one or more of the variables we can use arrange().

penguins |> arrange(bill_length_mm, bill_depth_mm)

## # A tibble: 344 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Adelie  Dream            32.1          15.5              188        3050 fema…
## 2 Adelie  Dream            33.1          16.1              178        2900 fema…
## 3 Adelie  Torge…           33.5          19                190        3600 fema…
## # … with 341 more rows, and 1 more variable: year <int>

This will sort smallest first. To reverse the sort order, use desc()

penguins |> arrange(desc(bill_length_mm), desc(bill_depth_mm))

## # A tibble: 344 × 8
##   species island bill_length_mm bill_depth_mm flipper_length_… body_mass_g sex  
##   <fct>   <fct>           <dbl>         <dbl>            <int>       <int> <fct>
## 1 Gentoo  Biscoe           59.6          17                230        6050 male 
## 2 Chinst… Dream            58            17.8              181        3700 fema…
## 3 Gentoo  Biscoe           55.9          17                228        5600 male 
## # … with 341 more rows, and 1 more variable: year <int>

Exercise

Sort the penguins data by

body mass
island and body mass, with the largest birds first

Hint

# hint 1
penguins |> 
  arrange(___, ___)

# hint 2
?desc

7.13 Counting rows with `count()` and `n()`

The function n can count how many rows there are in the each group (or the entire data frame if it is not grouped). It can be used with either mutate() or summarise().

penguins |> 
  group_by(species) |> 
  summarise(n = n())

## group_by: one grouping variable (species)

## summarise: now 3 rows and 2 columns, ungrouped

## # A tibble: 3 × 2
##   species       n
##   <fct>     <int>
## 1 Adelie      152
## 2 Chinstrap    68
## 3 Gentoo      124

Or with count()

penguins |> 
  count(species)

## count: now 3 rows and 2 columns, ungrouped

## # A tibble: 3 × 2
##   species       n
##   <fct>     <int>
## 1 Adelie      152
## 2 Chinstrap    68
## 3 Gentoo      124

count() is more concise, but group_by() and summarise() is useful when you need to calculate more variables (for example mean and standard deviation).

Exercise

From the penguins data, find

how many penguins are there of each species
how many penguins are there of each species in each island

Hint

penguins |> 
  count(___, ___)

# or
penguins |> 
  group_by(___) |> 
  summarise(___ = n())

7.14 Common problems

7.14.1 Non standard names

Ideally column names should follow the standard rules for naming objects in R - UPPER and lower case letters, numbers, “.” and "_" with the first character being a letter (or a dot if you want an invisible object). Sometimes when you import data, it has non-standard names with spaces or extra characters. If you need to refer to a column name that doesn’t follow the rules, you need to enclose it with back-ticks.

df <- tibble(`Region/Country` = "Norway", value = 42)
df

## # A tibble: 1 × 2
##   `Region/Country` value
##   <chr>            <dbl>
## 1 Norway              42

df |> rename(region_country = `Region/Country`)

## rename: renamed one variable (region_country)

## # A tibble: 1 × 2
##   region_country value
##   <chr>          <dbl>
## 1 Norway            42

It is sometimes best to rename these columns to make them easier to refer to. janitor::clean_names() is very efficient for making easy-to-use names.

7.15 Resources

stat545
R for data science (Online copy of book)
dplyr cheatsheet

Contributors

Richard J. Telford

6 Tidying data with tidyr

8 Working with multiple tables in dplyr

7 Working with single tables in dplyr

7.0.1 Load the package

7.0.2 More feedback tidylog

7.1 The penguins dataset

7.2 Selecting columns with select()

Exercise

7.2.1 select() helpers

Exercise

7.3 Renaming columns with rename

7.4 Moving columns with relocate()

7.5 Filtering rows with filter()

7.5.1 Filtering on multiple criteria

7.5.2 Common errors

Exercise

7.6 Slicing the data with slice()

7.7 Distinct rows with distinct()

Exercise

7.8 Random rows

7.9 Mutating and adding columns with mutate

Exercise

7.10 Summarising data with summarise()

Exercise

7.10.1 Summarising multiple columns

7.11 Grouping data with group_by

Exercise

7.12 Sorting with arrange()

Exercise

7.13 Counting rows with count() and n()

Exercise

7.14 Common problems

7.14.1 Non standard names

7.15 Resources

Contributors

7 Working with single tables in `dplyr`

7.0.2 More feedback `tidylog`

7.1 The `penguins` dataset

7.2 Selecting columns with `select()`

7.2.1 `select()` helpers

7.3 Renaming columns with `rename`

7.4 Moving columns with `relocate()`

7.5 Filtering rows with `filter()`

7.6 Slicing the data with `slice()`

7.7 Distinct rows with `distinct()`

7.9 Mutating and adding columns with `mutate`

7.10 Summarising data with `summarise()`

7.11 Grouping data with `group_by`

7.12 Sorting with `arrange()`

7.13 Counting rows with `count()` and `n()`