plot.mwd: Use plot on an mwd object.

Description

Plots the wavelet coefficients of a mwd class object.

Usage

# S3 method for mwd
plot(x, first.level = 1, main = "Wavelet Decomposition Coefficients",
        scaling = "compensated", rhlab = FALSE, sub = x$filter$name,
	NotPlotVal = 0.05, xlab = "Translate", ylab = "Resolution level",
	return.scale = TRUE, colour = (2:(npsi + 1)), ...)

Value

Axis labels for each resolution level unless return.scale=F when NULL is returned. The axis values are the maximum of the absolute value of the coefficients at that resolution level. They are returned because they are sometimes hard to read on the plot.

Arguments

x

The mwd object whose coefficients you wish to plot.

first.level

The first resolution level to begin plotting at. This argument can be quite useful when you want to supress some of the coarser levels in the diagram.

main

The main title of the plot.

scaling

How you want the coefficients to be scaled. The options are: "global" - one scale factor is chosen for the whole plot. The scale factor depends on the coefficient to be included on the plot that has the largest absolute value. The global option is useful when comparing coefficients that might appear anywhere in the plot; "by.level" - a scale factor is chosen for each resolution level in the plot. The scale factor for a level depends on the coefficient in that level that has the largest absolute value. The "by.level" option is useful when you wish to compare coefficients within a resolution level.

The other option is "compensated" which is the same as "global" except for that finer scales' coefficients are scaled up by a factor of SQRT(2) for compensated. This latter options is sometimes useful.

rhlab

If T then a set of labels is produced on the right hand axis. The axis labels in this case refer to the scale factors used to scale each level and correspond to value of the largest coefficient (in absolute value) in each scale (when scaling=="by.level") or absolutely (when scaling="global"). If the rhlab argument is FALSE then no right hand axis labels are produced.

sub

A subtitle for the plot.

NotPlotVal

Doesn't seem to be implemented.

xlab

A title for the x-axis

ylab

A title for the y-axis

return.scale

If true (default) the scale for each resolution level is returned

colour

A vector of length mwd$npsi, the values of which are the colours used to plot the coefficients, one for each distinct type of wavelet (with apologies to our American cousins for spelling colour correctly!)

...

other arguments to be supplied to plot.

RELEASE

Author

G P Nason

Details

Produces a plot similar to the ones in Donoho and Johnstone, 1994.

Wavelet coefficients for each resolution level are plotted one above the other, with the high resolution coefficients at the bottom, and the low resolution at the top. Each vector is represented by mwd$npsi lines one for each element in the coefficient vector. If colour is supported by the device each element will be represented by a different coulour. The coefficients are plotted using the segment function, with a large positive coefficient being plotted above an imaginary horizontal centre line, and a large negative coefficient plotted below it. The position of a coefficient along a line is indicative of the wavelet basis function's translate number.

The resolution levels are labelled on the left-hand side axis, and the maximum values of the absolute values of the coefficients for the particular level form the right-hand side axis.

The levels of coefficients can be scaled in three ways. If you are not interested in comparing the relative scales of coefficients from different levels, then the default scaling option, "by.level" is what you need. This computes the maximum of the absolute value of the coefficients at a particular level and scales the so that the fit nicely onto the plot. For this option, each level is scaled DIFFERENTLY. To obtain a uniform scale for all the levels specify the "global" option to the scaling argument. This will allow you to make inter-level comparisons.

Examples

Run this code

#
# Generate some test data
#
test.data <- example.1()$y
if (FALSE) ts.plot(test.data)
#
# Decompose test.data with multiple wavelet transform and
# plot the wavelet coefficients
#
tdmwd <- mwd(test.data)
if (FALSE) plot(tdmwd)
#[1] 1.851894 1.851894 1.851894 1.851894 1.851894 1.851894 1.851894
#
# You should see a plot with wavelet coefficients like in
# plot.wd but at each coefficient position
# there are two coefficients in two different colours one for each of
# the wavelets at that position.
#
# Note the scale for each level is returned by the function.

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