Reads out the X-axis values array.
The X-axis values array is the frequency, power or time values
array depending on the trace setup. The array contains real values.
The array size is N, where N is the number of measurement points.
For the n–th point, where n from 1 to N:
<numeric n> the X-axis value;
(Query only)
CALCulate<Ch>[:SELected]:DATA:XAXis? - the active trace of channel,
CALCulate<Ch>:TRACe<Tr>:DATA:XAXis? - the trace <Tr> of channel,
<Ch>={[1]|2|...16}
<Tr>={[1]|2|...16}