Data Wrangling
with dplyr and tidyr
Cheat Sheet
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Syntax - Helpful conventions for wrangling
dplyr::tbl_df(iris)
Converts data to tbl class. tbl’s are easier to examine than
data frames. R displays only the data that fits onscreen:
dplyr::glimpse(iris)
Information dense summary of tbl data.
utils::View(iris)
View data set in spreadsheet-like display (note capital V).
Source: local data frame [150 x 5]
Sepal.Length Sepal.Width Petal.Length
1 5.1 3.5 1.4
2 4.9 3.0 1.4
3 4.7 3.2 1.3
4 4.6 3.1 1.5
5 5.0 3.6 1.4
.. ... ... ...
Variables not shown: Petal.Width (dbl),
Species (fctr)
dplyr::%>%
Passes object on le hand side as first argument (or .
argument) of function on righthand side.
"Piping" with %>% makes code more readable, e.g.
iris %>%
group_by(Species) %>%
summarise(avg = mean(Sepal.Width)) %>%
arrange(avg)
x %>% f(y) is the same as f(x, y)
y %>% f(x, ., z) is the same as f(x, y, z )
Reshaping Data - Change the layout of a data set
Subset Observations (Rows)
Subset Variables (Columns)
F
M
A
Each variable is saved
in its own column
F
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Each observation is
saved in its own row
In a tidy
data set:
&
Tidy Data - A foundation for wrangling in R
Tidy data complements R’s vectorized
operations. R will automatically preserve
observations as you manipulate variables.
No other format works as intuitively with R.
M
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*
tidyr::gather(cases, "year", "n", 2:4)
Gather columns into rows.
tidyr::unite(data, col, ..., sep)
Unite several columns into one.
dplyr::data_frame(a = 1:3, b = 4:6)
Combine vectors into data frame
(optimized).
dplyr::arrange(mtcars, mpg)
Order rows by values of a column
(low to high).
dplyr::arrange(mtcars, desc(mpg))
Order rows by values of a column
(high to low).
dplyr::rename(tb, y = year)
Rename the columns of a data
frame.
tidyr::spread(pollution, size, amount)
Spread rows into columns.
tidyr::separate(storms, date, c("y", "m", "d"))
Separate one column into several.
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dplyr::filter(iris, Sepal.Length > 7)
Extract rows that meet logical criteria.
dplyr::distinct(iris)
Remove duplicate rows.
dplyr::sample_frac(iris, 0.5, replace = TRUE)
Randomly select fraction of rows.
dplyr::sample_n(iris, 10, replace = TRUE)
Randomly select n rows.
dplyr::slice(iris, 10:15)
Select rows by position.
dplyr::top_n(storms, 2, date)
Select and order top n entries (by group if grouped data).
<
Less than
!=
Not equal to
>
Greater than
%in%
Group membership
==
Equal to
is.na
Is NA
<=
Less than or equal to
!is.na
Is not NA
>=
Greater than or equal to
&,|,!,xor,any,all
Boolean operators
Logic in R - ?Comparison, ?base::Logic
dplyr::select(iris, Sepal.Width, Petal.Length, Species)
Select columns by name or helper function.
Helper functions for select - ?select
select(iris, contains("." ))
Select columns whose name contains a character string.
select(iris, ends_with("Length"))
Select columns whose name ends with a character string.
select(iris, everything())
Select every column.
select(iris, matches(". t ." ))
Select columns whose name matches a regular expression.
select(iris, num_range("x", 1:5))
Select columns named x1, x2, x3, x4, x5.
select(iris, one_of(c("Species", "Genus")))
Select columns whose names are in a group of names.
select(iris, starts_with("Sepal"))
Select columns whose name starts with a character string.
select(iris, Sepal.Length:Petal.Width)
Select all columns between Sepal.Length and Petal.Width (inclusive).
select(iris, -Species)
Select all columns except Species.
Learn more with browseVignettes(package = c("dplyr", "tidyr")) • dplyr 0.4.0• tidyr 0.2.0 • Updated: 1/15
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devtools::install_github("rstudio/EDAWR") for data sets
dplyr::group_by(iris, Species)
Group data into rows with the same value of Species.
dplyr::ungroup(iris)
Remove grouping information from data frame.
iris %>% group_by(Species) %>% summarise(…)
Compute separate summary row for each group.
Combine Data Sets
Group Data
Summarise Data
Make New Variables
ir
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dplyr::summarise(iris, avg = mean(Sepal.Length))
Summarise data into single row of values.
dplyr::summarise_each(iris, funs(mean))
Apply summary function to each column.
dplyr::count(iris, Species, wt = Sepal.Length)
Count number of rows with each unique value of
variable (with or without weights).
dplyr::mutate(iris, sepal = Sepal.Length + Sepal. Width)
Compute and append one or more new columns.
dplyr::mutate_each(iris, funs(min_rank))
Apply window function to each column.
dplyr::transmute(iris, sepal = Sepal.Length + Sepal. Width)
Compute one or more new columns. Drop original columns.
Summarise uses summary functions, functions that
take a vector of values and return a single value, such as:
Mutate uses window functions, functions that take a vector of
values and return another vector of values, such as:
window
function
summary
function
dplyr::first
First value of a vector.
dplyr::last
Last value of a vector.
dplyr::nth
Nth value of a vector.
dplyr::n
# of values in a vector.
dplyr::n_distinct
# of distinct values in
a vector.
IQR
IQR of a vector.
min
Minimum value in a vector.
max
Maximum value in a vector.
mean
Mean value of a vector.
median
Median value of a vector.
var
Variance of a vector.
sd
Standard deviation of a
vector.
dplyr::lead
Copy with values shied by 1.
dplyr::lag
Copy with values lagged by 1.
dplyr::dense_rank
Ranks with no gaps.
dplyr::min_rank
Ranks. Ties get min rank.
dplyr::percent_rank
Ranks rescaled to [0, 1].
dplyr::row_number
Ranks. Ties got to first value.
dplyr::ntile
Bin vector into n buckets.
dplyr::between
Are values between a and b?
dplyr::cume_dist
Cumulative distribution.
dplyr::cumall
Cumulative all
dplyr::cumany
Cumulative any
dplyr::cummean
Cumulative mean
cumsum
Cumulative sum
cummax
Cumulative max
cummin
Cumulative min
cumprod
Cumulative prod
pmax
Element-wise max
pmin
Element-wise min
iris %>% group_by(Species) %>% mutate(…)
Compute new variables by group.
x1
x2
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x3
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=
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x2
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Mutating Joins
Filtering Joins
Binding
Set Operations
dplyr::le_join(a, b, by = "x1")
Join matching rows from b to a.
a
b
dplyr::right_join(a, b, by = "x1")
Join matching rows from a to b.
dplyr::inner_join(a, b, by = "x1")
Join data. Retain only rows in both sets.
dplyr::full_join(a, b, by = "x1")
Join data. Retain all values, all rows.
x1
x2
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1
B
2
x1
x2
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3
y
z
dplyr::semi_join(a, b, by = "x1")
All rows in a that have a match in b.
dplyr::anti_join(a, b, by = "x1")
All rows in a that do not have a match in b.
dplyr::intersect(y, z)
Rows that appear in both y and z.
dplyr::union(y, z)
Rows that appear in either or both y and z.
dplyr::setdiff(y, z)
Rows that appear in y but not z.
dplyr::bind_rows(y, z)
Append z to y as new rows.
dplyr::bind_cols(y, z)
Append z to y as new columns.
Caution: matches rows by position.
RStudio® is a trademark of RStudio, Inc. • CC BY RStudio • info@rstudio.com • 844-448-1212 • rstudio.com Learn more with browseVignettes(package = c("dplyr", "tidyr")) • dplyr 0.4.0• tidyr 0.2.0 • Updated: 1/15devtools::install_github("rstudio/EDAWR") for data sets