One of the ideas that I had was to allow users to leave offset in link empty to automatically map data in y to each x.
At first my thought was to just map all data of y within the interval of subsequent measurements in x, but this is probably confusing because you can map it in two ways (forwards or backwards in time).
An alternative approach to match for each x exactly one measurement of y, namely the one closest in time. However, the question remains how useful this actually is.