On Sat, 21 Mar 2020 20:01:30 -0700 Thomas Subia via R-help <r-help using r-project.org> wrote: > Serial_test is a pass, when all of the Meas_test are pass for a given > serial. Else Serial_test is a fail. Use by/tapply in base R or dplyr::group_by if you prefer tidyverse packages. -- Best regards, Ivan