Quantile Plot for LMS Quantile Regression

Plots the quantiles associated with a LMS quantile regression.

Usage

plotqtplot.lmscreg(fitted.values, object, newdata = NULL,
    percentiles = object@misc$percentiles, lp = NULL,
    add.arg = FALSE, y = if (length(newdata)) FALSE else TRUE,
    spline.fit = FALSE, label = TRUE, size.label = 0.06,
    xlab = NULL, ylab = "",
    pch = par()$pch, pcex = par()$cex, pcol.arg = par()$col,
    xlim = NULL, ylim = NULL,
    llty.arg = par()$lty, lcol.arg = par()$col, llwd.arg = par()$lwd,
    tcol.arg = par()$col, tadj = 1, ...)

Arguments

fitted.values

Matrix of fitted values.

object

A VGAM quantile regression model, i.e., an object produced by modelling functions such as vglm and vgam with a family function beginning with "lms.", e.g., lms.yjn.

newdata

Data frame at which predictions are made. By default, the original data are used.

percentiles

Numerical vector with values between 0 and 100 that specify the percentiles (quantiles). The default is to use the percentiles when fitting the model. For example, the value 50 corresponds to the median.

lp

Length of percentiles.

add.arg

Logical. Add the quantiles to an existing plot?

y

Logical. Add the response as points to the plot?

spline.fit

Logical. Add a spline curve to the plot?

label

Logical. Add the percentiles (as text) to the plot?

size.label

Numeric. How much room to leave at the RHS for the label. It is in percent (of the range of the primary variable).

xlab

Caption for the x-axis. See par.

ylab

Caption for the x-axis. See par.

pch

Plotting character. See par.

pcex

Character expansion of the points. See par.

pcol.arg

Color of the points. See the col argument of par.

xlim

Limits of the x-axis. See par.

ylim

Limits of the y-axis. See par.

llty.arg

Line type. Line type. See the lty argument of par.

lcol.arg

Color of the lines. See the col argument of par.

llwd.arg

Line width. See the lwd argument of par.

tcol.arg

Color of the text (if label is TRUE). See the col argument of par.

tadj

Text justification. See the adj argument of par.

...

Arguments passed into the plot function when setting up the entire plot. Useful arguments here include main and las.

Details

The above graphical parameters offer some flexibility when plotting the quantiles.

Value

The matrix of fitted values.

References

Yee, T. W. (2004). Quantile regression via vector generalized additive models. Statistics in Medicine, 23, 2295–2315.

Author

Thomas W. Yee

Note

While the graphical arguments of this function are useful to the user, this function should not be called directly.

See also

qtplot.lmscreg.

Examples

if (FALSE) { # \dontrun{
fit <- vgam(BMI ~ s(age, df = c(4,2)), lms.bcn(zero = 1), data = bmi.nz)
qtplot(fit)
qtplot(fit, perc = c(25,50,75,95), lcol = "blue", tcol = "blue", llwd = 2)
} # }