How dose Piwik check 'Returning visitor' by log analytics

Hi.

I import log files to Piwik (Nov. 29 and Nov. 30 2014) .
In ‘Returning Visit’ report, it shows no visit.

https://drive.google.com/file/d/0B-UAIad0QmxrVGhFNUwwY1ZiRUE/view?usp=sharing

There are visitor they have same IP & U/A in log file.

Why that?

Even if one year passes, I contribute it once again because it is the same situation (ver.2.15.0).

By log-analytics, How does Piwik judge ‘Return Visits’?
Unlike tag analysis, there is very little number of Return Visits by the log analysis.

Return visits is the number of visit by the visitor whom I visited more than twice.
Is this right?

Hi there,

See how Piwik determines Unique/Returning visitors: How does Piwik detect unique and returning visitors? (with User ID, Visitor ID from cookie and/or fingerprint) - Analytics Platform - Matomo