How to Apply the dimnames() Function in R (2 Examples)

In this post you’ll learn how to get and set the dimension names of a data set using the dimnames() function in the R programming language.

Example Data

data(iris)                                     # Example data
head(iris)
#   Sepal.Length Sepal.Width Petal.Length Petal.Width Species
# 1          5.1         3.5          1.4         0.2  setosa
# 2          4.9         3.0          1.4         0.2  setosa
# 3          4.7         3.2          1.3         0.2  setosa
# 4          4.6         3.1          1.5         0.2  setosa
# 5          5.0         3.6          1.4         0.2  setosa
# 6          5.4         3.9          1.7         0.4  setosa

Example 1: Get Dimnames of Data Frame Object

dimnames(iris)                                 # Retrieve names of dimensions
# [[1]]
#   [1] "1"   "2"   "3"   "4"   "5"   "6"   "7"   "8"   "9"   "10"  "11"  "12"  "13"  "14"  "15"  "16"  "17"  "18"  "19"  "20"  "21"  "22"  "23"  "24"  "25"  "26"  "27"  "28"  "29"  "30"  "31"  "32"  "33"  "34"  "35"  "36" 
#  [37] "37"  "38"  "39"  "40"  "41"  "42"  "43"  "44"  "45"  "46"  "47"  "48"  "49"  "50"  "51"  "52"  "53"  "54"  "55"  "56"  "57"  "58"  "59"  "60"  "61"  "62"  "63"  "64"  "65"  "66"  "67"  "68"  "69"  "70"  "71"  "72" 
#  [73] "73"  "74"  "75"  "76"  "77"  "78"  "79"  "80"  "81"  "82"  "83"  "84"  "85"  "86"  "87"  "88"  "89"  "90"  "91"  "92"  "93"  "94"  "95"  "96"  "97"  "98"  "99"  "100" "101" "102" "103" "104" "105" "106" "107" "108"
# [109] "109" "110" "111" "112" "113" "114" "115" "116" "117" "118" "119" "120" "121" "122" "123" "124" "125" "126" "127" "128" "129" "130" "131" "132" "133" "134" "135" "136" "137" "138" "139" "140" "141" "142" "143" "144"
# [145] "145" "146" "147" "148" "149" "150"
# 
# [[2]]
# [1] "Sepal.Length" "Sepal.Width"  "Petal.Length" "Petal.Width"  "Species"

Example 2: Set Dimnames of Data Frame Object

dimnames(iris) <- list(paste0("r_", 1:150),    # Specify names of dimensions
                       paste0("x_", 1:5))
head(iris)
#     x_1 x_2 x_3 x_4    x_5
# r_1 5.1 3.5 1.4 0.2 setosa
# r_2 4.9 3.0 1.4 0.2 setosa
# r_3 4.7 3.2 1.3 0.2 setosa
# r_4 4.6 3.1 1.5 0.2 setosa
# r_5 5.0 3.6 1.4 0.2 setosa
# r_6 5.4 3.9 1.7 0.4 setosa

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