HH: ci.plot – R documentation

Become an expert in R — Interactive courses, Cheat Sheets, certificates and more!

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[, 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>

Examples

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

HH

Statistical Analysis and Data Display: Heiberger and Holland

v3.1-43

GPL (>= 2)

Authors

Richard M. Heiberger

Initial release

2020-11-27