[R] cumsum function to determine plankton phenology

Apologies for the empty email earlier! I have species abundance data sampled at a weekly frequency or sometimes monthly depending on the year. The goal is to identify the dates in an annual cycle in which the cumulative abundance of a species reaches some threshold. Here's an example of the data

[R] cumsum formula to determine plankton phenology

Dear R-users -- -- Heather Anne --- Heather A. Wright, PhD candidate Ecology and Evolution of Plankton Stazione Zoologica Anton Dohrn Villa Comunale 80121 - Napoli, Italy website