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Encoder for Quantitative Variables

Source: R/numeric_encoder.R
numeric.encoder.Rd

numeric.encoder() creates an encoder function for a quantitative variable. This encoder can then be used to convert a numeric vector into a design matrix using either piecewise linear or one-hot interval encoding, which are core components for modeling effects in a MID model.

numeric.frame() is a helper function to create a "numeric.frame" object that defines the encoding scheme.

Usage

numeric.encoder(
  x,
  k,
  type = 1L,
  encoding.digits = NULL,
  tag = "x",
  frame = NULL,
  weights = NULL
)

numeric.frame(
  reps = NULL,
  breaks = NULL,
  type = NULL,
  encoding.digits = NULL,
  tag = "x"
)

Arguments

x

a numeric vector to be encoded.

k

an integer specifying the coarseness of the encoding. If not positive, all unique values of x are used as knots or bins.

type

an integer (1 or 0) specifying the encoding method (see the "details" section).

encoding.digits

an integer specifying the rounding digits for the piecewise linear encoding (type = 1).

tag

the name of the variable.

frame

a "numeric.frame" object or a numeric vector that explicitly defines the knots or breakes for the encoding.

weights

an optional numeric vector of sample weights for x.

reps

a numeric vector to be used as the representative values (knots).

breaks

a numeric vector to be used as the binning breaks.

Value

numeric.encoder() returns an object of class "encoder". This is a list containing the following components:

frame

a "numeric.frame" object containing the encoding information.

encode

a function to convert a numeric vector x into a dummy matrix.

n

the number of encoding levels (i.e., columns in the design matrix).

type

a character string describing the encoding type: "linear", "constant", or "null".

numeric.frame() returns a "numeric.frame" object containing the encoding information.

Details

The primary purpose of the encoder is to transform a single numeric variable into a design matrix for the MID model's linear system formulation. The output of the encoder depends on the type argument.

When type = 1, the variable's effect is modeled as a piecewise linear function with k knots including both ends. For each value, the encoder finds the two nearest knots and assigns a weight to each, based on its relative position. This results in a design matrix where each row has at most two non-zero values that sum to 1. This approach creates a smooth, continuous representation of the effect.

When type = 0, the variable's effect is modeled as a step function by dividing its range into k intervals (bins). The encoder determines which interval each value falls into and assigns a 1 to the corresponding column in the design matrix, with all other columns being 0. This results in a standard one-hot encoded matrix and creates a discrete, bin-based representation of the effect.

See also

factor.encoder

Examples

# Create an encoder for a quantitative variable
data(iris, package = "datasets")
enc <- numeric.encoder(x = iris$Sepal.Length, k = 5L, tag = "Sepal.Length")
enc
#> 
#> Linear encoder with 5 knots
#> 
#> Frame:
#>   Sepal.Length
#> 1          4.3
#> 2          5.1
#> 3          5.8
#> 4          6.4
#> 5          7.9
#> 

# Encode a numeric vector with NA and Inf
enc$encode(x = c(4:8, NA, Inf))
#>        4.3   5.1       5.8       6.4 7.9
#> [1,] 1.000 0.000 0.0000000 0.0000000 0.0
#> [2,] 0.125 0.875 0.0000000 0.0000000 0.0
#> [3,] 0.000 0.000 0.6666667 0.3333333 0.0
#> [4,] 0.000 0.000 0.0000000 0.6000000 0.4
#> [5,] 0.000 0.000 0.0000000 0.0000000 1.0
#> [6,] 0.000 0.000 0.0000000 0.0000000 0.0
#> [7,] 0.000 0.000 0.0000000 0.0000000 1.0

# Create an encoder with a pre-defined encoding frame
frm <- numeric.frame(breaks = c(3, 5, 7, 9), type = 0L)
enc <- numeric.encoder(x = iris$Sepal.Length, frame = frm)
enc$encode(x = c(4:8, NA, Inf))
#>      [-Inf, 5) [5, 7) [7, Inf)
#> [1,]         1      0        0
#> [2,]         0      1        0
#> [3,]         0      1        0
#> [4,]         0      0        1
#> [5,]         0      0        1
#> [6,]         0      0        0
#> [7,]         0      0        1

# Create an encoder with a numeric vector specifying the knots
enc <- numeric.encoder(x = iris$Sepal.Length, frame = c(3, 5, 7, 9))
enc$encode(x = c(4:8, NA, Inf))
#>        3   5   7   9
#> [1,] 0.5 0.5 0.0 0.0
#> [2,] 0.0 1.0 0.0 0.0
#> [3,] 0.0 0.5 0.5 0.0
#> [4,] 0.0 0.0 1.0 0.0
#> [5,] 0.0 0.0 0.5 0.5
#> [6,] 0.0 0.0 0.0 0.0
#> [7,] 0.0 0.0 0.0 1.0