Selecting within complex shape

Hello,

In the Gridded Dataset tutorial page (https://holoviews.org/getting_started/Gridded_Datasets.html), it is specified that ROIs are often more complex polygons but for simplicity’s sake we will use simple rectangular ROIs specified as the left, bottom, right and top coordinate of a bounding box. Then I understand all the examples below, but I would like to select pixels of a time series of maps using shapes from a shapefile.

Currently, I have a 3D dataset (longitude, latitude and time for some values) and a shapefile that I read into a geoviews shape. I would like to average the values within the each of the shapes of the shapefile over time. I understand I should use the select and aggregate methods, but I cannot see how to get a complex shape into select and I could not find how to do this on the web.

Thank you very much for the help and thanks for Holoviz. I am new to this, but it is pretty awesome.
Cheers,
Romain