Random Samples and Permutations.

Take a sample of the specified size from the elements of x with or without replacement.

# S4 method for hyperSpec
sample(x, size, replace = FALSE, prob = NULL)

isample(x, size = nrow(x), replace = FALSE, prob = NULL)

# S4 method for data.frame
sample(x, size, replace = FALSE, prob = NULL, drop = FALSE)

# S4 method for matrix
sample(x, size, replace = FALSE, prob = NULL, drop = FALSE)

Arguments

x	The hyperSpec object, data.frame or matrix to sample fromto sample from
size	positive integer giving the number of spectra (rows) to choose.
replace	Should sampling be with replacement?
prob	A vector of probability weights for obtaining the elements of the vector being sampled.
drop	see base::drop(): by default, do not drop dimensions of the result

Value

a hyperSpec object, data.frame or matrix with size rows for sample, and an integer vector for isample that is suitable for indexing (into the spectra) of x.

vector with indices suitable for row-indexing x

See also

base::sample()

Author

C. Beleites

Examples

sample(flu, 3)
#> hyperSpec object
#>    3 spectra
#>    3 data columns
#>    181 data points / spectrum
#> wavelength: lambda/nm [numeric] 405.0 405.5 ... 495 
#> data:  (3 rows x 3 columns)
#>    1. spc: I[fl]/"a.u." [matrix, array181] 167.26667 93.14433 ... 45.25633 
#>    2. filename: filename [character] rawdata/flu5.txt rawdata/flu3.txt rawdata/flu1.txt 
#>    3. c: c / (mg / l) [numeric] 0.25 0.15 0.05 

plot(flu, col = "darkgray")
plot(sample(flu, 3), col = "red", add = TRUE)

plot(flu, col = "darkgray")
plot(sample(flu, 3, replace = TRUE),
  col = "#0000FF80", add = TRUE,
  lines.args = list(lwd = 2)
)
isample(flu, 3)
#> [1] 6 4 2
isample(flu, 3, replace = TRUE)
#> [1] 3 2 1
isample(flu, 8, replace = TRUE)
#> [1] 3 2 5 3 6 5 1 1
sample(cars, 2)
#>    speed dist
#> 34    18   76
#> 50    25   85
sample(matrix(1:24, 6), 2)
#>      [,1] [,2] [,3] [,4]
#> [1,]    3    9   15   21
#> [2,]    4   10   16   22