create base class MeasurementData for ADC_Result and Accumulation

doc/manual.rst

@@ -759,6 +759,36 @@ Example:
 - **get_ymax()**
    Returns maximum of y
 
+- **get_ymean(start=None, stop=None)**
+   Returns the mean value of every channel. If *start* and *stop* are given,
+   they select a time interval in seconds. The calculation uses raw values
+   for **timesignal** and the public mean values for **accu**.
+
+   Example:
+
+   .. code-block:: python
+
+      means = timesignal.get_ymean(start=1e-6, stop=4e-6)
+      means = accu.get_ymean()
+
+- **get_phase(pos=None)**
+   Returns the phase in degrees from the first two channels at the first
+   sample or at time *pos* in seconds.
+
+   Example:
+
+   .. code-block:: python
+
+      phase = timesignal.get_phase(pos=1e-6)
+
+- **get_ymin_channels()/get_ymax_channels()**
+   Return NumPy arrays containing the minimum or maximum for each channel.
+   **get_ymin()** and **get_ymax()** return the corresponding global extrema.
+
+- **get_yrms()/get_ystd()**
+   Return NumPy arrays containing the RMS or population standard deviation
+   for each channel.
+
 
 
 .. bibliography::