dg_glf

vector of standardized scores from the continuous ordinal scale, 0<<code>v</code>

vector of 2 elements: <code>B</code>, the slope of the curve, and <code>T</code>, the symmetry of the curve.

Derivative of the generalized logistic function as in Richards (1959):
$$g'(v) = \frac{T}{B}  \frac{1}{v(1-v^{T})}$$

logistic

derivative

Richards

function.

generalized

A regression framework for response variables which are continuous self-rating scales such as the Visual Analog Scale (VAS) used in pain assessment, or the Linear Analog Self-Assessment (LASA) scales in quality of life studies. These scales  measure subjects' perception of an intangible quantity, and cannot be handled as ratio variables because of their inherent nonlinearity. We treat them as ordinal variables, measured on a continuous scale. A function (the g function, currently the generalized logistic function) connects the scale with an underlying continuous latent  variable.  The link function is the inverse of the CDF of the assumed underlying distribution of the latent variable. Currently the logit link, which corresponds to a standard logistic distribution, is implemented.

dg_glf: Derivative of generalized logistic g function

Description

Usage

Arguments

Value

References

See Also