errorsINx: Simulate data for straight line regression, with "errors in...

In DAAG: Data Analysis and Graphics Data and Functions

Simulate data for straight line regression, with "errors in x".

Description

Simulates $y-$ and $x-$values for the straight line regression model, but with $x-$values subject to random measurement error, following the classical “errors in x” model. Optionally, the x-values can be split into two groups, with one group shifted relative to the other

Usage

errorsINx(mu = 12.5, n = 200, a = 15, b = 1.5, SDx=2, SDyerr = 1.5,
           timesSDx=(1:5)/2.5, gpfactor=if(missing(gpdiff))FALSE else TRUE,
           gpdiff=if(gpfactor) 1.5 else 0, layout=NULL,
           parset = simpleTheme(alpha = 0.75, col = c("black","gray45"),
             col.line = c("black","gray45"), lwd=c(1,1.5), pch=c(1,2),
           lty=c(1,2)), print.summary=TRUE, plotit=TRUE, xrelation="same")

Arguments

mu	Mean of $z$
n	Number of points
a	Intercept in model where $z$ is measured without error
b	Slope in model where $z$ is measured without error
SDx	SD of $z$-values, measured without error
SDyerr	SD of error term in y where $z$ is measured without error
timesSDx	SD of measurement error is timesSDx, as a multiple of SDx
gpfactor	Should x-values be split into two groups, with one shifted relative to the other?
gpdiff	Amount of shift of one group of z-values relative to the other
layout	Layout for lattice graph, if requested
parset	Parameters to be supplied to the lattice plot, if any
print.summary	Print summary information on fits?
plotit	logical: plot the data?
xrelation	character: sets the x-axis relation component of scales to "same" or "free" or (though this does not make make sense here) "sliced".

Details

The argument timesSDx can be a numeric vector. One set of $x$-values that are contaminated with measurement error is simulated for each element of timesSDx.

Value

gph	the trellis graphics object
mat	A matrix, with length(timesSDx)+2 columns. Values of $z$ are in the first column. There is one further column (x with error) for each element of timesSDx, followed by a column for $y$. If there is a grouping variable, a further column identifies the groups.

Author(s)

John Maindonald

References

Data Analysis and Graphics Using R, 3rd edn, Section 6.7

Examples

library(lattice)
errorsINx()
errorsINx(gpdiff=2, timesSDx=1.25, SDyerr=2.5, n=80)

DAAG documentation built on May 29, 2024, 9:13 a.m.