apply_shift_scale

A function that is used to shift x values to positive values if it contains
negative or zero values.If all values of x are positive then the original
values of x is returned without shifting but scaled if the scaling factor is
not equal to 1. If x has already been shifted and scaled then the function does
nothing.

Multivariable fractional polynomial algorithm simultaneously selects variables and functional forms in both generalized linear models and Cox proportional hazard models. Key references for this algorithm are Royston and Altman (1994)<doi:10.2307/2986270> and Sauerbrei and Royston (2008, ISBN:978-0-470-02842-1). In addition, it can model a 'sigmoid' relationship between variable x and an outcome variable y using the approximate cumulative distribution transformation proposed by Royston (2014) <doi:10.1177/1536867X1401400206>. This feature distinguishes it from a standard fractional polynomial function, which lacks the ability to achieve such modeling.

Edwin Kipruto

mfp2

Multivariable Fractional Polynomial Models with Extensions

Michael Kammer

Patrick Royston

Willi Sauerbrei

apply_shift_scale function

<dl><dt>x</dt>
<dd>A vector of predictor variable</dd>
<dt>scale</dt>
<dd>scaling factors for x of interest. Must be positive integers.
Default is NULL and scaling factors are automatically estimated using
find_scale_factor() function else it uses user supplied scaling factors. If no scaling
is needed just use scale = 1</dd>
<dt>shift</dt>
<dd>adjustment factors required for shifting x to positive
values. Default is NULL and adjustment factors are estimated automatically
using find_shift_factor() function</dd></dl>

Arguments

Shift and scale vector x — apply_shift_scale

<dl>

<dt>x</dt>
<dd>A vector of predictor variable</dd>


<dt>scale</dt>
<dd>scaling factors for x of interest. Must be positive integers.
Default is NULL and scaling factors are automatically estimated using
find_scale_factor() function else it uses user supplied scaling factors. If no scaling
is needed just use scale = 1</dd>


<dt>shift</dt>
<dd>adjustment factors required for shifting x to positive
values. Default is NULL and adjustment factors are estimated automatically
using find_shift_factor() function</dd>

</dl>

apply_shift_scale: Shift and scale vector x

Description

Usage

Value

Arguments

Examples