method you are using requires the DataFrame’s index to be numerical in order to tell which row is nearest to the one being interpolated at a time. In KNIME, however, the index of the DataFrame is of the form
Row2, etc. (so, string-valued). If you expect the index to be equally spaced, you could simply use the
'linear' interpolation method instead of
'nearest'. If you do require a notion of distance between your rows (for example, because rows in the input have been skipped like so:
Row2 would be closer to
Row3), you must first convert the index into a numerical form.
More information about pandas’s
interpolate function can also be found here.