Hi everyone! I am new to R and need some help!

I am trying to make a for loop to sum precipitation values in one day. However, some days the increments of data are not equal (some days have data every 15 minutes other days have data every 10 minutes). I have converted the dates into a floating number in my excel file to help, but I do not know how to write a for loop that will read these numbers in excel.

For example, for data every 15 minutes I would write for(k in 1:96) to sum data that day. But some days have data every 15 minutes, while others is every 10 minutes, so this loop will not properly sum the days.