ci.plot: Plot confidence and prediction intervals for simple linear...

Description Usage Arguments Value Note Author(s) See Also Examples

Description

The data, the least squares line, the confidence interval lines, and the prediction interval lines for a simple linear regression (lm(y ~ x)) are displayed. Tick marks are placed at the location of xbar, the x-value of the narrowest interval.

Usage

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ci.plot(lm.object, ...)

## S3 method for class 'lm'
ci.plot(lm.object,
        xlim=range(data[, x.name]),
        newdata,
        conf.level=.95,
        data=model.frame(lm.object),
        newfit,
        ylim,
        pch=19,
        lty=c(1,3,4,2),
        lwd=2,
        main.cex=1,
        main=list(paste(100*conf.level,
          "% confidence and prediction intervals for ",
          substitute(lm.object), sep=""), cex=main.cex), ...
        )

Arguments

lm.object

Linear model for one y and one x variable.

xlim

xlim for plot. Default is based on data from which lm.object was constructed.

newdata

data.frame containing data for which predictions are wanted. The variable name of the column must be identical to the name of the predictor variable in the model object. Defaults to a data.frame containing a vector spanning the range of observed data. User-specified values are appended to the default vector.

conf.level

Confidence level for intervals, defaults to .95

data

data extracted from the lm.object

newfit

Constructed data.frame containing the predictions,confidence interval, and prediction interval for the newdata.

ylim

ylim for plot. Default is based on the constructed prediction interval.

pch

Plotting character for observed points.

lty, lwd

Line types and line width for fit and intervals.

main.cex

Font size for main title.

main

Main title for plot

...

Additional arguments to be passed to panel function.

Value

"trellis" object containing the plot.

Note

The predict.lm functions in S-Plus and R differ. The S-Plus function can produce both confidence and prediction intervals with a single call. The R function produces only one of them in a single call. Therefore the default calculation of newfit within the function depends on the system.

Author(s)

Richard M. Heiberger <rmh@temple.edu>

See Also

lm, predict.lm

Examples

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tmp <- data.frame(x=rnorm(20), y=rnorm(20))
tmp.lm <- lm(y ~ x, data=tmp)
ci.plot(tmp.lm)

Example output

Loading required package: lattice
Loading required package: grid
Loading required package: latticeExtra
Loading required package: RColorBrewer
Loading required package: multcomp
Loading required package: mvtnorm
Loading required package: survival
Loading required package: TH.data
Loading required package: MASS

Attaching package: 'TH.data'

The following object is masked from 'package:MASS':

    geyser

Loading required package: gridExtra

HH documentation built on Nov. 28, 2020, 9:06 a.m.

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