[rrd-users] Daily consumption

[Simon Hobson]

Bram Langen <bram.langen at mail.com> wrote:

> ... but for full flexibility and data analysis (such as comparing same period year over year) I let the Raspberry Pi write the counter values once a day to a text file. Every so often I import the CSV data into MS-Excel, allowing any data comparison you want.

You can (AIUI) do time period comparisons by using the time offset functions.
I've not done it myself, but AIUI you can create two CDEFs and offset one of them by (say) 365 days, then plot them on the same graph.