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This example demonstrates the use of wavInit and wavAddSample for waveform display, and how to place labels using the label function.

Any button can be used to display a waveform.
The call to wavInit sets up certain specially named attributes in the button.

`View demoWaveform.psi in your browser <_static/demoWaveform.psi>`_ or
:download:`Download demoWaveform.psi <_static/demoWaveform.psi>`

Setting the waveform area
   | The waveform is displayed in the insets rectangle
   | ``wavButton.insets = { .25, .1, 0, .1 };`` leaves room for x axis labels on the bottom and a general label of the graph on top, as well as a big area to the left for labeling the y axis.
   | ``wavButton.color = { 0, 1, 0, .1 };`` gives the waveform area a pale green background.

Y axis labels
   | ``labtopy = label(wavButton, "top Y", { 0, 1 }, { -1, 0 });`` and
   | ``labboty = label(wavButton, "bot Y", { 0, 0 }, { -1, 0 });``
   | are used to label the y axis with the maximum and minimum of the range of values displayed in the waveform.  (The "top Y" and "bot Y" are just placeholders; the actual values are set later to make the program easier to read.) The x position, 0, places the labels to the left of the waveform display, and the x offset, -1, left-justifies the text so it doesn't cover the display.
   | The y positions, 1 and 0, place the texts at the top and bottom of the display area, and the y offset of zero vertically centers the text on the top and bottom edges of the display area.