Ticket: Find out why our user graphs have huge spikes in Q2/2011
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1. Plot single variables of daily user estimate

- reported directory requests
- ratio of written directory bytes of the directory mirrors reporting
  directory requests compared to all written directory bytes
- daily users

On a machine with the metrics database from metrics-web installed, edit
and run daily-users.R.

  $ R --slave -f daily-users.R


2. Plot directory bytes estimate

  $ R --slave -f dir-bytes-estimate.R

