TkApprox: Plot a set of data in a Tk window and interactively move...

In TeachingDemos: Demonstrations for Teaching and Learning

Description

This function plots a dataset in a Tk window then places 3 lines on the plot which show a predicted y value for the given x value. The lines can be clicked on and dragged to new x-values with the predicted y-values automatically updating. A table at the bottom of the graph shows the differences between the pairs of x-values and y-values.

Usage

TkApprox(x, y, type = "b", snap.to.x = FALSE, digits = 4,
  cols = c("red", "#009900", "blue"), xlab = deparse(substitute(x)),
  ylab = deparse(substitute(y)), hscale = 1.5, vscale = 1.5,
  wait = TRUE, ...)

Arguments

x	The x-values of the data, should be sorted
y	The corresponding y-values of the data
type	Type of plot (lines, points, both) passed to plot
snap.to.x	If True then the lines will snap to x-values (can be changed with a checkbox in the Tk window)
digits	Number of significant digits to display (passed to format)
cols	Vector of 3 colors, used for the reference lines
xlab	Label for x-axis
ylab	Label for y-axis
hscale	Horizontal Scale of the plot, passed to tkrplot
vscale	Vertical Scale of the plot, passed to tkrplot
wait	Should R wait for the window to be closed
...	Additional parameters passed to plot

Details

This provides an interactive way to explore predictions from a set of x and y values. Internally the function approxfun is used to make the predictions.

The x-value of the 3 reference lines can be changed by clicking and dragging the line to a new position. The x and y values are shown in the margins of the graph. Below the graph is a table with the differences (absolute value) between the pairs of points.

This can be used to find peaks/valleys in trends and to see how they differ from starting points, other peaks/valleys, etc..

Value

If wait is FALSE then an invisible NULL is returned, if wait is TRUE then an invisible list with the x and y values of the 3 reference lines is returned.

Author(s)

Greg Snow [e-mail]

See Also

approxfun, TkSpline

Examples

if(interactive()) {
  with(ccc, TkApprox(Time2,Elevation))
}

TeachingDemos documentation built on April 2, 2020, 3:01 a.m.