Extracting a Data Portion

The {portion} R package offers convenient tools to extract data portions from various objects:

1. works for vector, matrix, data.frame, and list objects

2. the relative portion size can be selected

3. allows to extract first, last, random, similar or dissimilar data

4. can portion row- and column-wise

5. provides selected indices as an attribute

6. preserves object attributes

Installation

You can install the released version from CRAN with:

install.packages("portion")

Example

Can portion a vector:

x <- c(1, 1, 2, 2)
portion(x, proportion = 0.5, how = "similar")
#> [1] 1 1
#> attr(,"indices")
#> [1] 1 2
portion(x, proportion = 0.5, how = "dissimilar")
#> [1] 1 2
#> attr(,"indices")
#> [1] 1 3

Can portion a matrix:

x <- matrix(LETTERS[1:24], nrow = 4)
portion(x, proportion = 0.5, how = "first")
#>      [,1] [,2] [,3] [,4] [,5] [,6]
#> [1,] "A"  "E"  "I"  "M"  "Q"  "U" 
#> [2,] "B"  "F"  "J"  "N"  "R"  "V" 
#> attr(,"indices")
#> [1] 1 2
portion(x, proportion = 0.5, how = "first", byrow = FALSE)
#>      [,1] [,2] [,3]
#> [1,] "A"  "E"  "I" 
#> [2,] "B"  "F"  "J" 
#> [3,] "C"  "G"  "K" 
#> [4,] "D"  "H"  "L" 
#> attr(,"indices")
#> [1] 1 2 3

Can portion a data.frame:

x <- as.data.frame(diag(8))
portion(x, proportion = 0.3, how = "random")
#>   V1 V2 V3 V4 V5 V6 V7 V8
#> 1  1  0  0  0  0  0  0  0
#> 3  0  0  1  0  0  0  0  0
#> 7  0  0  0  0  0  0  1  0
portion(x, proportion = 0.3, how = "random", byrow = FALSE)
#>   V1 V2 V5
#> 1  1  0  0
#> 2  0  1  0
#> 3  0  0  0
#> 4  0  0  0
#> 5  0  0  1
#> 6  0  0  0
#> 7  0  0  0
#> 8  0  0  0

Can work on a list:

x <- list(1:5, diag(3), data.frame(1:3, 2:4))
portion(x, proportion = 0.5, how = "last")
#> [[1]]
#> [1] 3 4 5
#> attr(,"indices")
#> [1] 3 4 5
#> 
#> [[2]]
#>      [,1] [,2] [,3]
#> [1,]    0    1    0
#> [2,]    0    0    1
#> attr(,"indices")
#> [1] 2 3
#> 
#> [[3]]
#>   X1.3 X2.4
#> 2    2    3
#> 3    3    4