IDyOM Project

h1. Working with viewpoints

A number of functions are provided to help the user work with viewpoints and viewpoint data.

The [[List of Viewpoints|available viewpoints]] are described in "Pearce [2005]":http://webprojects.eecs.qmul.ac.uk/marcusp/papers/Pearce2005.pdf and implemented in the <code>derived-viewpoints/</code> directory in amuse-viewpoints. It is easy to implement new viewpoints, the examples in that file and [[Adding Viewpoints]] should help you get started.

h2. Inspecting viewpoint values

<code>music-data:composition-viewpoint</code> will return the viewpoint values for a specific composition.  For example, for composition 3 of dataset 0, pitch interval has the following values:

<pre>

CL-USER> (music-data:composition-viewpoint 0 3 'cpint)

(0 -300 0 -200 -200 0 -100 100 200 -200 500 0 0 0 -100 100 200 -700 0 0 0 400 0

 100 200 0 -700 700 0 200 -200 -300 -400 200 -200)

</pre>

And the linked viewpoint <code>'(cpint ioi)</code> has:

<pre>

CL-USER> (music-data:composition-viewpoint 0 3 '(cpint ioi))

((0 12) (-300 12) (0 12) (-200 12) (-200 24) (0 12) (-100 12) (100 12) (200 12)

 (-200 24) (500 12) (0 12) (0 12) (0 12) (-100 12) (100 12) (200 12) (-700 60)

 (0 12) (0 12) (0 12) (400 12) (0 12) (100 12) (200 12) (0 24) (-700 12)

 (700 24) (0 12) (200 12) (-200 12) (-300 12) (-400 12) (200 12) (-200 12))

</pre>

Similarly, <code>music-data:dataset-viewpoint</code> returns the values for all compositions in a specific dataset, as a list of lists:

<pre>

CL-USER> (music-data:dataset-viewpoint 0 'cpint)

((-300 -200 0 0 0 500 0 0 400 0 0 0 0 -200 -200 0 0 -300 -200 0 500 400 0 -200

  ...)

 (300 -300 100 -300 200 -200 -300 -400 1200 -300 100 -300 0 200 100 200 -300

  ...)

...)

 </pre>

You can also count the frequency of each symbol in a dataset (currently only implemented for numeric viewpoints):

<pre>

CL-USER> (utils:numeric-frequencies (music-data:dataset-viewpoint 0 'cpint))

((-1400 . 3) (-1200 . 24) (-1100 . 1) (-1000 . 5) (-900 . 28) (-800 . 58)

 (-700 . 125) (-500 . 251) (-400 . 324) (-300 . 589) (-200 . 1408) (-100 . 341)

 (0 . 2127) (100 . 414) (200 . 1318) (300 . 432) (400 . 309) (500 . 435)

 (700 . 120) (800 . 11) (900 . 38) (1000 . 12) (1200 . 25) (1400 . 1)

 (1900 . 1))

</pre>