If experimenters did not collect data for an exercise (fx Synch), R by default shows an obscure error that does not make it clear what is wrong.
A much nicer way to handle this (which would cause less confusion), would be to tell the students that there currently has not been collected any data for the chosen e-mail address.
If experimenters did not collect data for an exercise (fx Synch), R by default shows an obscure error that does not make it clear what is wrong.
A much nicer way to handle this (which would cause less confusion), would be to tell the students that there currently has not been collected any data for the chosen e-mail address.