windowedFit function

Linear fit in a running window

This is an internal function used by the afmContactPoint

and afmDetachPoint functions. It computes the slopes of a linear fit to the data in a window of a given radius. This function should not be used directly unless by experienced users.

windowedFit(X, width)

Arguments

• X: Least squares matrix on the form [1 z Force], according to input parameters in function lm.fit
• width: Width of the window for the local regression (in vector position units)

Returns

OUT A vector of length nrow(X)-2*width, containing with the slopes of the fits.

Examples

n <- 100
x <- seq(0,2*pi,length.out = n)
y = sin(x)+0.1*rnorm(n)
X <- matrix(c(rep(1,n),x,y),nrow = n,ncol = 3)
width <- 5
b <- windowedFit(X,width)
plot(x[(width+1):(n-width)],b,xlab = "x",ylab = "y",type = "l")
lines(x,y,col = "red")
legend("bottomleft",c("Slopes","Signal"),col = c(1,2),lty = 1)