# err.breakage: Error function for estimated tip geometry In breakage: SICM pipette tip geometry estimation

## Description

Calculates the residual sum of squares error between measured resistance data and the predicted resistances for a given set of model parameters.

## Usage

 `1` ```err.breakage(params, data, rho = 51, l = 1000) ```

## Arguments

 `params` A vector of the 2 tip geometry parameters, where `params[1]` is the half-cone angle in radians, and `params[2]` is the initial inner radius in microns. `data` The recorded data as an XY list or data frame, where `data\$x` contains the breakage distances in microns and `data\$y` holds the corresponding resistances in megohms. `rho` Resistivity of the filler solution, in ohm centimetres. The default value of 51 ohm cm corresponds to a 150 mM solution of KCl. `l` The initial length of the pipette tip. Because the resistance is dominated by the narrower tip region, the precise value of this is not usually important provided it is much greater than the breakage distance.

## Details

This function quantifies the error between a posited model of the pipette tip geometry and the results actually recorded. It is organised for minimisation by the standard `optim` function, and is used as such within `fit.breakage`. It is not expected to be much used outside that context.

## Value

The calculated error value.

Matthew Caldwell

## See Also

`fit.breakage`

## Examples

 ```1 2 3 4 5 6 7 8``` ```# estimate breakage data for one geometry brks <- 0.2 * 0:10 res <- resist.breakage(brks, theta=4*pi/180, r=0.05, rho=64) dat <- list(x=brks, y=res) # compare it to different geometry err.breakage(c(2*pi/180, 0.1), dat, rho=64) err.breakage(c(6*pi/180, 0.02), dat, rho=64) ```

breakage documentation built on May 1, 2019, 11:30 p.m.