This depends on the period over which you aggregate transactions. DSB recommends aggregating over no more than a minute.
For example, consider the situation if you aggregate transactions over a minute. Each minute, you store the transactions aggregated over that minute as Transactions per Minute (TPM) for that minute.
Suppose you perform your calculation daily with your stored TPM values. You have 24 x 60 = 1440 TPM values.
For each second in a given minute, Transactions per second (TPS) is the same:
TPS = (TPM for that minute)/60
The average daily TPM is:
Average daily TPM = sum(TPM for entire day)/(24 x 60)
The average daily TPS is:
Average daily TPS = (average daily TPM)/60
Peak TPS for that day is:
Peak TPS = (peak TPM on that day)/60