Useful R functions (detailed)

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Sandbox vectors

Let’s define some vectors which can be used for demonstrations:

manyNumbers <- sample( 1:1000, 20 )
manyNumbers

 [1] 867  66 335 550 274 471 705 812 300 703 140 348 106 574 767 848 749 464 593 790

manyNumbersWithNA <- sample( c( NA, NA, NA, manyNumbers ) )
manyNumbersWithNA

 [1]  66 550 471 300  NA 593 140 274  NA 106  NA 767 464 703 705 790 749 867 348 574 812 848 335

duplicatedNumbers <- sample( 1:5, 10, replace = TRUE )
duplicatedNumbers

 [1] 5 4 5 4 3 2 5 5 1 3

letters

 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y"
[26] "z"

LETTERS

 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y"
[26] "Z"

mixedLetters <- c( sample( letters, 5 ), sample( LETTERS, 5 ) )
mixedLetters

 [1] "m" "n" "l" "k" "r" "J" "Z" "V" "E" "R"

Are all/any elements TRUE

• Input: logical vector
• Output: single logical value
• Task: try, understand what happens when you use manyNumbersWithNA instead of manyNumbers.

all( manyNumbers <= 1000 )

[1] TRUE

all( manyNumbers <= 500 )

[1] FALSE

any( manyNumbers > 1000 )

[1] FALSE

any( manyNumbers > 500 )

[1] TRUE

all( !is.na( manyNumbers ) )

[1] TRUE

any( is.na( manyNumbers ) )

[1] FALSE

Which elements are TRUE

Input: logical vector Output: vector of numbers (positions)

which( manyNumbers > 900 )

integer(0)

which( manyNumbersWithNA > 900 )

integer(0)

which( is.na( manyNumbersWithNA ) )

[1]  5  9 11

Filtering vector elements

• Input: any vector and filtering condition
• Output: elements of the input vector
• Note: several ways to get the same effect

manyNumbers[ manyNumbers > 900 ] # indexing by logical vector

integer(0)

manyNumbers[ which( manyNumbers > 900 ) ] # indexing by positions

integer(0)

somePositions <- which( manyNumbers > 900 )
manyNumbers[ somePositions ]

integer(0)

Are some elements among other elements

• Input: two vectors
• Output: a logical vector corresponding to the first input vector

"A" %in% LETTERS

[1] TRUE

c( "X", "Y", "Z" ) %in% LETTERS

[1] TRUE TRUE TRUE

all( c( "X", "Y", "Z" ) %in% LETTERS )

[1] TRUE

all( mixedLetters %in% LETTERS )

[1] FALSE

any( mixedLetters %in% LETTERS )

[1] TRUE

mixedLetters[ mixedLetters %in% LETTERS ]

[1] "J" "Z" "V" "E" "R"

mixedLetters[ !( mixedLetters %in% LETTERS ) ]

[1] "m" "n" "l" "k" "r"

manyNumbers %in% 300:600

 [1] FALSE FALSE  TRUE  TRUE FALSE  TRUE FALSE FALSE  TRUE FALSE FALSE  TRUE FALSE  TRUE FALSE FALSE
[17] FALSE  TRUE  TRUE FALSE

which( manyNumbers %in% 300:600 )

[1]  3  4  6  9 12 14 18 19

sum( manyNumbers %in% 300:600 )

[1] 8

Pick one of two (three) depending on condition

• Input: a logical vector and two vectors additional vectors (for TRUE, for FALSE)
• Output: elements of the additional vectors
• Note: it can take care of NAs

if_else( manyNumbersWithNA >= 500, "large", "small" )

 [1] "small" "large" "small" "small" NA      "large" "small" "small" NA      "small" NA      "large"
[13] "small" "large" "large" "large" "large" "large" "small" "large" "large" "large" "small"

if_else( manyNumbersWithNA >= 500, "large", "small", "UNKNOWN" )

 [1] "small"   "large"   "small"   "small"   "UNKNOWN" "large"   "small"   "small"   "UNKNOWN" "small"  
[11] "UNKNOWN" "large"   "small"   "large"   "large"   "large"   "large"   "large"   "small"   "large"  
[21] "large"   "large"   "small"  

# here integer 0L is needed instead of real 0.0 
# manyNumbersWithNA contains integer numbers and the method complains
if_else( manyNumbersWithNA >= 500, manyNumbersWithNA, 0L ) 

 [1]   0 550   0   0  NA 593   0   0  NA   0  NA 767   0 703 705 790 749 867   0 574 812 848   0

Duplicates and unique elements

• Input: a vector

unique( duplicatedNumbers )

[1] 5 4 3 2 1

unique( c( NA, duplicatedNumbers, NA ) )

[1] NA  5  4  3  2  1

duplicated( duplicatedNumbers )

 [1] FALSE FALSE  TRUE  TRUE FALSE FALSE  TRUE  TRUE FALSE  TRUE

Positions of max/min elements

which.max( manyNumbersWithNA )

[1] 18

manyNumbersWithNA[ which.max( manyNumbersWithNA ) ]

[1] 867

which.min( manyNumbersWithNA )

[1] 1

manyNumbersWithNA[ which.min( manyNumbersWithNA ) ]

[1] 66

range( manyNumbersWithNA, na.rm = TRUE )

[1]  66 867

Sorting/ordering of vectors

manyNumbersWithNA

 [1]  66 550 471 300  NA 593 140 274  NA 106  NA 767 464 703 705 790 749 867 348 574 812 848 335

sort( manyNumbersWithNA )

 [1]  66 106 140 274 300 335 348 464 471 550 574 593 703 705 749 767 790 812 848 867

sort( manyNumbersWithNA, na.last = TRUE )

 [1]  66 106 140 274 300 335 348 464 471 550 574 593 703 705 749 767 790 812 848 867  NA  NA  NA

sort( manyNumbersWithNA, na.last = TRUE, decreasing = TRUE )

 [1] 867 848 812 790 767 749 705 703 593 574 550 471 464 348 335 300 274 140 106  66  NA  NA  NA

manyNumbersWithNA[1:5]

[1]  66 550 471 300  NA

order( manyNumbersWithNA[1:5] )

[1] 1 4 3 2 5

rank( manyNumbersWithNA[1:5] )

[1] 1 4 3 2 5

sort( mixedLetters )

 [1] "E" "J" "k" "l" "m" "n" "r" "R" "V" "Z"

Ranking of vectors

manyDuplicates <- sample( 10:15, 10, replace = TRUE )
rank( manyDuplicates )

 [1] 2.5 5.0 5.0 1.0 9.0 7.0 9.0 5.0 9.0 2.5

rank( manyDuplicates, ties.method = "min" )

 [1] 2 4 4 1 8 7 8 4 8 2

rank( manyDuplicates, ties.method = "random" )

 [1]  2  5  6  1  9  7  8  4 10  3

Rounding numbers

v <- c( -1, -0.5, 0, 0.5, 1, rnorm( 10 ) )
v

 [1] -1.0000000 -0.5000000  0.0000000  0.5000000  1.0000000 -0.3600554 -0.1645529 -1.2719354  1.2917038
[10] -0.0121865  2.0913009 -0.3896672  0.9755700 -0.7491305  0.8087457

round( v, 0 )

 [1] -1  0  0  0  1  0  0 -1  1  0  2  0  1 -1  1

round( v, 1 )

 [1] -1.0 -0.5  0.0  0.5  1.0 -0.4 -0.2 -1.3  1.3  0.0  2.1 -0.4  1.0 -0.7  0.8

round( v, 2 )

 [1] -1.00 -0.50  0.00  0.50  1.00 -0.36 -0.16 -1.27  1.29 -0.01  2.09 -0.39  0.98 -0.75  0.81

floor( v )

 [1] -1 -1  0  0  1 -1 -1 -2  1 -1  2 -1  0 -1  0

ceiling( v )

 [1] -1  0  0  1  1  0  0 -1  2  0  3  0  1  0  1

Naming vector elements

heights <- c( Amy = 166, Eve = 170, Bob = 177 )
heights

Amy Eve Bob 
166 170 177 

names( heights )

[1] "Amy" "Eve" "Bob"

names( heights ) <- c( "AMY", "EVE", "BOB" )
heights

AMY EVE BOB 
166 170 177 

heights[[ "EVE" ]]

[1] 170

Generating grids

expand_grid( x = c( 1:3, NA ), y = c( "a", "b" ) )

# A tibble: 8 × 2
      x y    
  <int> <chr>
1     1 a    
2     1 b    
3     2 a    
4     2 b    
5     3 a    
6     3 b    
7    NA a    
8    NA b    

Generating combinations

combn( c( "a", "b", "c", "d", "e" ), m = 2, simplify = TRUE )

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "a"  "a"  "a"  "a"  "b"  "b"  "b"  "c"  "c"  "d"  
[2,] "b"  "c"  "d"  "e"  "c"  "d"  "e"  "d"  "e"  "e"  

combn( c( "a", "b", "c", "d", "e" ), m = 3, simplify = TRUE )

     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] "a"  "a"  "a"  "a"  "a"  "a"  "b"  "b"  "b"  "c"  
[2,] "b"  "b"  "b"  "c"  "c"  "d"  "c"  "c"  "d"  "d"  
[3,] "c"  "d"  "e"  "d"  "e"  "e"  "d"  "e"  "e"  "e"  

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