Macro: Xpand

This button duplicates the X-Axis button on the Daqarta toolbar. You can also toggle with ALT+X. When active, the X axis expands to the limits set by the Max and Min controls below it.

The expansion simply changes the spacing between data points for easier viewing; it does not increase actual resolution.

There are separate eXpand states and Max and Min limits for waveform, Histogram, and Spectrum modes, as well as for X-Log Spectrum. There is also a Spectrogram ( Sgram) eXpand which operates on the Y (frequency) axis, as explained later in this topic.

Besides setting the Max and Min limits manually and hitting this eXpand button, you can also expand the region between the cursors at any time by hitting ALT+CTRL+X. If eXpand is not active, that will activate it, and Max and Min will be forced to the values under the solid and dotted cursors. Whichever cursor is at the lowest X-value will set Min, and the highest will set Max.

Additionally, you can scroll Min with the horizontal arrow buttons at the left end of the X axis, and scroll Max with those at the right end. Alternatively, you can drag the X axis left or right with the mouse. Dragging to the left moves Min down, while dragging to the right moves Max up. To move Min up, start dragging to the left and then without lifting the button drag to the right. To drag Max down, start dragging to the right and then to the left.

eXpand is toggled on automatically by these scrolling or dragging operations. Use the X-Axis button ( ALT+X) or the eXpand button to toggle it back off.

In waveform mode, the eXpand state is active by default to show only the first 512 points of the waveform, even though 1024 data points are collected. That's because all screens can resolve 512 horizontal pixels, even at 640x480 resolution.

If eXpand is set to show more points than the screen supports, it simply means that some of the points will overlap. The cursors will still move one point at a time using the arrow keys, which will be seen on the readouts, even if the cursor doesn't appear to move because both points share the same horizontal pixel position. Positioning the cursors with the mouse will still work, but you won't be able to get the finest resolution.

In Spectrum modes, the same 1024 points yield 512 spectral lines, so there is normally no issue regarding screen resolution. However, regardless of the screen, in X-Log mode the high frequencies will typically be compressed as a result of the logarithmic axis. Points will then overlap and the same issues with cursor position will arise. Just use the cursor keys for finest control.

Spectrogram (Sgram) eXpand operates on the Y (frequency) axis. Its operation is somewhat different from other modes in that the expansion is fixed at a factor of two, and Max and Min are interlocked to control which part of the frequency range will be seen.

For example, with a 44100 Hz sample rate, the unexpanded vertical axis runs from 0 to 22006.93 Hz... the same as the unexpanded X axis in Spectrum mode. "Unexpanded" is really a misnomer for the Spectrogram, since it is actually compressed to show 512 spectral lines as 256 vertical pixels. So each vertical pixel is the combination of two spectral lines.

When eXpand is active, each pixel represents only one spectral line, so the range is only 256 lines. The default is Min = 0 so Max is just under 11000 Hz... 255 lines higher, since each spectral line is 43.07 Hz at this sample rate. You can change Min or Max, but they will always track at 255 lines apart.

Most of the energy in speech, music, most animal sounds, and most machine vibrations falls in the default range.

As with the X-axis eXpands, you can use the mouse to drag the Spectrogram Y axis. This will immediately toggle eXpand on if it was not on already. Then you can just slide the frequency range of interest as needed. Since there is really only one independent variable here, dragging is much easier than it is for the X-axis modes; you will never need to start in one direction and reverse motion, just drag directly.

When you make changes to the eXpand state or Max/Min limits of the Spectrogram, note that the changes only apply from the current time point onward. Any prior time points that may be visible on the screen are unchanged until they are eventually overwritten.

Macro Notes:

Xpand=1 sets eXpand mode, Xpand=0 turns it off, and Xpand=x toggles between on and off.

See also X-Axis Control Dialog

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