generate_powers_fp {mfp2}

Function that generates a matrix of FP powers for any degree

Description

Function that generates a matrix of FP powers for any degree

Usage

generate_powers_fp(degree = NULL, powers = NULL)

generate_powers_acd(degree = NULL, powers = NULL)

Arguments

degree

The degree of fractional polynomial. For example, degree = 1 is FP1 and returns 8 powers; degree 2 is FP2 and returns 36 pairs of powers; degree 3 is FP3 and returns 120 triples of powers, and so on. If the ACD transformation is used, this degree is assumed to be 2.

powers

the set of allowed powers for the fractional polynomials. Default is NULL and the set (-2, -1, -0.5, 0, 0.5, 1, 2, 3) is used.

Details

For FP powers, this function returns all combinations of the powers of length degree, that is all pairs in which each entry is taken from the set powers, but no pair is repeated (i.e. the order of the entries does not matter). Thus, for the default set of powers and degree 2, this function returns 36 combinations.

For ACD powers, this function simply returns all possible tuples of powers of length n. Thus, for the default set of powers, this function returns 8 possible powers, and for degree 2 it returns 64 pairs of powers. Higher degrees are not supported by the function. In case that degree = 0 or degree = 1, the first column of the matrix representing untransformed data are set to NA to indicate that the normal data do not play a role. Higher degrees than two are not supported.

Value

A matrix of powers with degree columns and rows depending on the degree. For ACD powers always a matrix with two columns. For normal fps each row will be sorted in increasing order (in alignment with how transform_vector_fp() processes the data).

Functions

• generate_powers_acd(): Function to generate acd powers.

Examples

powx <- c(-2, -1, -0.5, 0, 0.5, 1, 2, 3)
generate_powers_fp(degree = 2, powers = powx)
generate_powers_acd(degree = 2, powers = powx)