Seeing from the tags you've used in your question, we assume you're referring especially to bandwidth monitoring using SNMP.

PRTG Collects Raw Data

PRTG requests the current value provided by a device with each scanning interval. These usually are averaged data of a (very) small time period—e.g. a few seconds or minutes. In PRTG, these values are called raw data. Using PRTG's Reports functionality or the Historic Data function in a sensor's details view, you can create reports on raw data. However, when generating reports for longer time periods, PRTG will automatically set a greater averaging interval for performance reasons.

Raw data is available for at least one year (if not set otherwise in the data purging options in System Setup).

Alternatively to using the Reports or Historic Data functions, you can also use PRTG's API to obtain monitoring data and then process it in any application of your choice.

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For more information, please see How can I create reports of monitoring data? How can I export data?