HH (version 1.5)

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

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

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

## S3 method for class 'lm':
ci.plot(lm.object,
        xlim=range(data[,as.character(formula.lm[[3]])]),
        newdata=data.frame(seq(xlim[1], xlim[2], length=51)),
        conf.level=.95,
        data=model.frame(lm.object),
        newfit,
        ylim=range(newfit$pi.fit),
        pch=16,
        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. Defaults to vector spanning range of observed data.

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.

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.

See Also

lm, predict.lm

Examples

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