breakage (version 1.1-1)

breakage.plot: Plot a pipette breakage current or resistance relationship

Description

Calculates and plots a current-distance or resistance-distance relation from recorded current-position data during pipette tip breakage.

Usage

breakage.plot(x, time.limits = NULL, btm = find.bottom(x$Z), pch = 16, col = 1, lty = "solid", col.l = 2, plot.line = FALSE, f = median, mV = NA, ...)

Arguments

x

A data frame containing the experimental current and position traces. The frame should include a column named Z, containing the position in microns, and a column named pA, containing the recorded current in picoamps. If the time.limits parameter is specified, there must also be a column named s containing time information (typically in seconds, although the units are not used).

time.limits

An optional 2-element vector specifying lower and upper bounds in the s column of data to which the processing should be constrained.

btm

An optional vector of division points breaking the signal into segments. Typically this is obtained from the Z data by calling find.bottom.

pch

Symbol to use for plotting individual current/resistance measurements.

col

Colour to use for plotting the current/resistance points.

lty

Line type to use for plotting a regression line.

col.l

Colour to use for plotting a regression line.

plot.line

Whether to plot a regression line. By default this is not done, as a linear regression line corresponds poorly to the resistance behaviour. It may be a useful rough indicator when plotting only current data.

f

Function to use for determining the current between hops. By default the median is used, but in some cases it may make sense to use a different measure.

mV

The pipette potential at which the data were recorded. If not supplied, resistance cannot be calculated and the current data are graphed directly.

...

Other graphical parameters to be passed to the plot function.

Value

Z

The identified bottom of hop positions, in microns.

pA

The corresponding median (or other) current through the withdrawn pipette, in picoamps.

Mohm

The calculated pipette resistance in megohms. (Only present if mV was supplied.)

References

Caldwell, M., Del Linz, S. J. L., Smart, T. G. S. and Moss, G. W. J. 2012 Method for estimating the tip geometry of scanning ion conductance microscope pipets. Anal. Chem. 84(21):8980--8984

See Also

find.bottom

Examples

# load the example data set
data("break.data")
breakage.plot(break.data, mV=100)