I’m trying to join two dataframes in R, each of which has multiple repetitions of the same ID number. This is to be expected within the data and is not a data quality issue.

I’m trying to combine information from 3 different datasets (gonadosomatic indices, larval counts, and qPCR gene copy values) with common columns of Year, Week, Site, and Type (specifying sampling events). The datasets have approximately 4k, 50, and 500 rows in each, respectively. For each Year, Week, Site, and Type specification, the GSI data consists of 20 different data points, the plankton data consists of 1 data point, and the gene copy values are 12 data points. My plankton data also does not join with the other two.