Alex, Thanks for the feedback, I've clarified each point below.
Alex van den Bogaerdt wrote: > On Tue, Sep 05, 2006 at 02:01:03PM -0400, Dan Cech wrote: > >> However, when I'm displaying the graph for the current month, the >> PERCENT function is using all the unknown future values in the >> calculation > > sure > >> causing it to be incorrect. > > Why? In this case I don't mean incorrect from a mathematical standpoint, but in terms of the purpose of the report. > You seem to know about your "unknown" data. That means it isn't > as unknown as the name suggests... Yes, I can easily disregard it for reporting purposes, that's not the problem. My problem is that my employer requires display of a graph showing the data for the current calendar month, with the 95th percentile line overlaid. I'm attempting to figure out a solution to produce this without having to use a separate call to calculate the 95th and manually specify it for the graph, though it appears that this may be my only workable solution. >> As a very simplified example, say I'm 10 days into a month (with 20 days >> remaining) and the values so far look like this: >> >> 1,2,3,4,5,6,7,8,9,10 >> >> The 90th percentile should be 9 > > according to what/who ? The 90th percentile of the values above is 9. I understand that the PERCENT function will include the 20 UNKN values and produce the answer 7 which is also mathematically correct but 'incorrect' from the point of view of this particular application. >> I have looked through the documentation and can't find any mechanism >> which would allow me to restrict the PERCENT function to a specific date >> range (to exclude values in the future), or exclude NaN values. > > Why graph values in the future, you know this won't include useful data. See above, my employer requires that the graph show the calendar month. > try changing unknown into some known value, like zero or a very large > negative number This will have the same effect as UNKN, if I'm reading the relevant documentation correctly: Unknown values are considered lower than any finite number for this purpose so if this operator returns an unknown you have quite a lot of them in your data. Infinite numbers are lesser, or more, than the finite numbers and are always more than the Unknown numbers. (NaN < -INF < finite values < INF) It seems that the easiest method may be to pre-calculate the 95th percentile on just the known data and go from there, though I would like to avoid the added overhead of opening each RRD twice (these graphs can span up to 20 rrds) if possible. Regards, Dan -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://lists.ee.ethz.ch/rrd-users WebAdmin http://lists.ee.ethz.ch/lsg2.cgi
