afmZeroPointSlope function

Zero Force Point and Slope

This function finds the point of zero force (real contact point) and the slope of the contact part of the Force-Distance curve.

afmZeroPointSlope(afmdata, fstar = 0, segment = c("approach", "retract"))

Arguments

• afmdata: An afmdata object. It should be a valid afmdata object upon which the Contact Point and the baseline correction must have been calculated first (using functions afmContactPoint() and afmBaselineCorrection())
• fstar: Value such that fstar * sd is to be considered as zero Force, where sd is the standard deviation of Force at the basline. It takes fstar = 0 as default value, meaning that zero force is actually zero.
• segment: The segment on which everything is calculated.

Returns

An afmdata class variable which will consist on the original input afmdata variable plus a new list named Slopes with the following fields: Z0Point: Point of zero force. Slope: Slope of the best fit line in the contact part of the Force-Distance curve.

Examples

data <- afmReadJPK("force-save-JPK-2h.txt.gz", path = path.package("afmToolkit"))
data <- afmContactPoint(data, width = 20, mul1 = 1, mul2 = 20)
data <- afmDetachPoint(data, width = 40, mul1 = 3, mul2 = 40)
data <- afmBaselineCorrection(data)
data <- afmZeroPointSlope(data, segment = "approach")
## Not run:

plot(data, segment = "approach") + geom_vline(xintercept = data$Slopes$Z0Point, lty = 2)
## End(Not run)