Grafana is a cool data visualisation tool. You can even improve it by adding additional panels and plugins. The whole plugin directory can be found here: https://grafana.net/plugins.
I recommend the Histogram panel. Unfortunately you can’t do it directly from the GUI (at least not in the current version 3.0). However, installing on the Raspberry Pi is relatively simple:
cd /usr/share/grafana/public/app/plugins/panel sudo git clone https://github.com/mtanda/grafana-histogram-panel sudo service grafana-server restart