secant {DFA} R Documentation

## secant method for detection of crossover points

### Description

Applies the secant method for detection of crossover points on the log-log curve.

### Usage

secant(x,y,npoint,size_fit)


### Arguments

 x Vector of the decimal logarithm of the boxes sizes. y Vector of the decimal logarithm of the DFA calculated in each boxe. npoint Number of crossover points calculated on the log-log curve. size_fit Number of points of the two semi-curved fitted in the extremes of the log-log curve.

### Value

 position Position of the crossover point identified by the secant method.

### Author(s)

Victor Barreto Mesquita

### Examples

# Example with the data referring to the log fluctuation
#channel curve data calculated for an epileptic subject
#extracted in the Physionet platform.

library(DFA)
data("EEGsignal")
x<-EEGsignal$log10(boxes) y<-EEGsignal$log10(DFA)
plot(x,y,xlab="log10(boxes)",ylab="log10(DFA)")

secant(x,y,npoint=2,size_fit=8)

# Example with crossover point fixed in position=20.

library(DFA)
part1 <- seq(1,20)
part2 <- seq(20,1)
y = c(part1,part2)
x<-seq(1,40)
plot(x,y)
secant(x,y,npoint=1,size_fit=8)



[Package DFA version 0.9.0 Index]