Merge pull request #929 from PeterNSteinmetz/revRawIoDocs

Rev raw io docs

Author: samuelgarcia

doc/source/rawio.rst

@@ -114,8 +114,17 @@ Read signal chunks of data and scale them::
 
 
 There are 3 ways to select a subset of channels: by index (0 based), by id or by name.
-By index is not ambiguous 0 to n-1 (included), for some IOs channel_names (and sometimes channel_ids) have no guarantees to
-be unique, in such cases it would raise an error.
+By index is unambiguous 0 to n-1 (included), whereas for some IOs channel_names
+(and sometimes channel_ids) have no guarantees to
+be unique. In such cases, using names or ids may raise an error.
+
+A selected subset of channels which is passed to get_analog_signal_chunk, get_analog_signal_size,
+or get_analog_signal_t_start has the additional restriction that all such channels must have
+the same t_start and signal_size.
+
+Such subsets of channels may be available in specific RawIOs by using the
+get_group_signal_channel_indexes method, if the RawIO has defined separate
+group_ids for each group with those common characteristics.
 
 Example with BlackrockRawIO for the file FileSpec2.3001::
 

neo/rawio/baserawio.py

@@ -654,12 +654,32 @@ def _segment_t_stop(self, block_index, seg_index):
     ###
     # signal and channel zone
     def _get_signal_size(self, block_index, seg_index, channel_indexes):
+        """
+        Return the size of a set of AnalogSignals indexed by channel_indexes.
+
+        All channels indexed must have the same size and t_start.
+        """
         raise (NotImplementedError)
 
     def _get_signal_t_start(self, block_index, seg_index, channel_indexes):
+        """
+        Return the t_start of a set of AnalogSignals indexed by channel_indexes.
+
+        All channels indexed must have the same size and t_start.
+        """
         raise (NotImplementedError)
 
     def _get_analogsignal_chunk(self, block_index, seg_index, i_start, i_stop, channel_indexes):
+        """
+        Return the samples from a set of AnalogSignals indexed by channel_indexes.
+
+        All channels indexed must have the same size and t_start.
+
+        RETURNS
+        -------
+            array of samples, with each requested channel in a column
+        """
+
         raise (NotImplementedError)
 
     ###