NAME

spoke - Extract points from an auditory image which lie along aspoke (ie. radial line) of the spiral map of the auditory image.

CONTENTS

Syntax
Description
Options
Units Of Angle
Summary Statistics
Examples
Copyright

spoke [arguments] [file]

Read auditory image frames output by either gensai or genspl.(Note that their default options are different, particularly pwidth,nwidth, and dencf). The frames must be preceded by an AIM header.For each frame, extract a set of points and write them on the stdoutas binary shorts. The set of points lie along a spoke of the spiralmap of the auditory image. The location of the spoke in the spiralmap is specified as a sector of given orientation and angle.(See options theta and dtheta).

1. frames.

When the input consists of a cartoon of multiple framesthen single frames or a range of sequential frames may be selected from theinput using:

  frames=a[-b]

The upper limit ‘b’ is optional,and when it is missing then the range is a single frame,otherwise ‘a’ and ‘b’ are inclusive range limits.The strings "min" and "max" are recognised as extreme limits, otherwisethe values of ‘a’ and ‘b’ are frame numbers: 0,1,2,...

The frame selector may also take time units (s, or ms) to specify frames"closest" to the given time, being the frame number which is the greatestinteger multiple of the framestep (‘frstep_epn’ or ‘frstep_aid’) which doesnot exceed the given time, measured from the start of the input file.

2. Header.

When Header=on, the output is preceded by an AIM header appropriatefor genepn output. In this way, the output of the spoke program canbe plotted using genepn. For example:

  spoke Header=on file > file.epn  genepn useprevious=on file

The option flag:

  Header=off

causes the header to be suppressed from the output.

3. theta.

Theta is the angle of the sector which contains the spoke.It is the angle between the datum (which can be imagined as the 3 o’clockposition on the spiral plot) and the centre of the angle subtended by thesector.

Theta is given as a real number, appended with optional units.(See notes on units of angle, below). Theta can also take a specialvalue:

  theta=max

In this case, a sector of size dtheta (see below) is rotated in smallincrements around the spiral. At each step, the sum of the points withinthe sector at that angle is extracted. The sector with the maximum sumis output. The angle theta of this maximum sector is also printed onthe stderr.

The size of the small increments can be set using the silent optiondangle (delta angle). When dangle=1min, the search for the max sectoris through 60 sectors around the spiral.

4. dtheta.

Delta theta (dtheta) is the angle subtended by the sector, describingthe size of the sector. Delta theta is given as a real number, appendedwith optional units. (See notes on units of angle, below).

5. sectorstat.

The name of the function used to calculated the summary statistic ofpoints within the sector at a given radius from the centre of the spiral.Any of the available summary statistical functions can be used(see notes on summary statistics below).

6. spokestat.

The name of the function used to calculated the summary statistic ofeach spoke. This is the summary of the points at successive radii,which have already been summarised across the sector angle by sectorstat.Any of the available summary statistical functions canbe used (see notes on summary statistics below).

7. Silent options.

There are a few silent (ie. not commonly used) options which areexplained using:

  spoke help=all

Any of the angle options (theta, dtheta, dangle) may be given as a realnumber with appended units. If no units are appended, the number istaken to be a fraction of the unit circle. Otherwise, the list ofavailable units is: deg, min, rad, pi.

The list of available statistical functions is: mean, max, sum, cg.The cg (centre of gravity) function returns the mean of the inputvalues weighted by their position in the input array.The source code (spoke.c) contains details of how the list of functionscan easily be extended.

echo q | genspl output=stdout file | spoke theta=0 dtheta=10deg > file.epn  to plot the spoke:genepn useprevious=on file  or, alternatively:hdr file.epn | x11plot

Copyright (c) Applied Psychology Unit, Medical Research Council, 1995

Permission to use, copy, modify, and distribute this software without feeis hereby granted for research purposes, provided that this copyrightnotice appears in all copies and in all supporting documentation, and thatthe software is not redistributed for any fee (except for a nominalshipping charge). Anyone wanting to incorporate all or part of thissoftware in a commercial product must obtain a license from the MedicalResearch Council.

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