| correct.acrophase {cosinor2} | R Documentation |
Acrophase Correction
Description
Corrects the value of the acrophase parameter of the cosinor model, placing it in the appropriate quadrant.
Usage
correct.acrophase(x)
Arguments
x |
An object of the |
Details
The acrophase parameter of a cosinor model is found by solving an equation with inverse tangent of an expression which contains linearized cosinor parameters. However, multiple numeric entities may result in a same value of tangent and just calculating the inverse tangent may result with the wrong value of the acrophase. This function corrects the acrophase from the cosinor.lm object according to the procedure from Bingham et al. (1982).
More specifically, the acrophase is calculated as:
K + g * arctan \vert\frac{\gamma}{\beta}\vert
where values of K and g depend on the signs of \beta and \gamma and can be derived from the following table:
sign \beta | sign \gamma | K | g |
| + | + | 0 | -1 |
| + | - | -2\pi | 1 |
| - | + | -\pi | 1 |
| - | - | -\pi | -1 |
References
Bingham, C., Arbogast, B., Guillaume Cornélissen, G., Lee, J.K. & Halberg, F. (1982). Inferential Statistical Methods for Estimating and Comparing Cosinor Parameters. Chronobiologia, 9(4), 397-439.
Examples
fit.temperature<-cosinor.lm(Temperature~time(Time), period = 24, data = temperature_zg)
correct.acrophase(fit.temperature)