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] 517 986  85 829 144 108 536 644 348  81  17 507  42 979 155  91 280 301 585 949

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

 [1] 507  NA 108 585 144 348 517 301  81  42 536 829  91 949  17  85 979 986 155 280 644  NA  NA

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

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

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" "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" "Z"

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

 [1] "o" "s" "u" "k" "g" "O" "L" "U" "R" "Z"

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 )

[1]  2 14 20

which( manyNumbersWithNA > 900 )

[1] 14 17 18

which( is.na( manyNumbersWithNA ) )

[1]  2 22 23

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

[1] 986 979 949

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

[1] 986 979 949

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

[1] 986 979 949

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] "O" "L" "U" "R" "Z"

mixedLetters[ !( mixedLetters %in% LETTERS ) ]

[1] "o" "s" "u" "k" "g"

manyNumbers %in% 300:600

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

which( manyNumbers %in% 300:600 )

[1]  1  7  9 12 18 19

sum( manyNumbers %in% 300:600 )

[1] 6

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] "large" NA      "small" "large" "small" "small" "large" "small" "small" "small" "large" "large" "small" "large" "small" "small" "large" "large" "small" "small"
[21] "large" NA      NA     

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

 [1] "large"   "UNKNOWN" "small"   "large"   "small"   "small"   "large"   "small"   "small"   "small"   "large"   "large"   "small"   "large"   "small"   "small"  
[17] "large"   "large"   "small"   "small"   "large"   "UNKNOWN" "UNKNOWN"

# 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] 507  NA   0 585   0   0 517   0   0   0 536 829   0 949   0   0 979 986   0   0 644  NA  NA

Duplicates and unique elements

• Input: a vector

unique( duplicatedNumbers )

[1] 4 2 5 3

unique( c( NA, duplicatedNumbers, NA ) )

[1] NA  4  2  5  3

duplicated( duplicatedNumbers )

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

Positions of max/min elements

which.max( manyNumbersWithNA )

[1] 18

manyNumbersWithNA[ which.max( manyNumbersWithNA ) ]

[1] 986

which.min( manyNumbersWithNA )

[1] 15

manyNumbersWithNA[ which.min( manyNumbersWithNA ) ]

[1] 17

range( manyNumbersWithNA, na.rm = TRUE )

[1]  17 986

Sorting/ordering of vectors

manyNumbersWithNA

 [1] 507  NA 108 585 144 348 517 301  81  42 536 829  91 949  17  85 979 986 155 280 644  NA  NA

sort( manyNumbersWithNA )

 [1]  17  42  81  85  91 108 144 155 280 301 348 507 517 536 585 644 829 949 979 986

sort( manyNumbersWithNA, na.last = TRUE )

 [1]  17  42  81  85  91 108 144 155 280 301 348 507 517 536 585 644 829 949 979 986  NA  NA  NA

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

 [1] 986 979 949 829 644 585 536 517 507 348 301 280 155 144 108  91  85  81  42  17  NA  NA  NA

manyNumbersWithNA[1:5]

[1] 507  NA 108 585 144

order( manyNumbersWithNA[1:5] )

[1] 3 5 1 4 2

rank( manyNumbersWithNA[1:5] )

[1] 3 5 1 4 2

sort( mixedLetters )

 [1] "g" "k" "L" "o" "O" "R" "s" "u" "U" "Z"

Ranking of vectors

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

 [1]  1.5  4.0  1.5  7.0  7.0  4.0 10.0  7.0  4.0  9.0

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

 [1]  1  3  1  6  6  3 10  6  3  9

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

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

Rounding numbers

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

 [1] -1.00000000 -0.50000000  0.00000000  0.50000000  1.00000000  0.14869382 -1.39818942 -0.06505665  0.83037541  1.75082107  1.42230791  1.17252215 -1.44468445
[14] -0.71492889 -0.36219210

round( v, 0 )

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

round( v, 1 )

 [1] -1.0 -0.5  0.0  0.5  1.0  0.1 -1.4 -0.1  0.8  1.8  1.4  1.2 -1.4 -0.7 -0.4

round( v, 2 )

 [1] -1.00 -0.50  0.00  0.50  1.00  0.15 -1.40 -0.07  0.83  1.75  1.42  1.17 -1.44 -0.71 -0.36

floor( v )

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

ceiling( v )

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

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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