# [rrd-users] Re: Newbie - Values Entered over long periods

Alex van den Bogaerdt alex at slot.hollandcasino.nl
Wed Sep 5 01:51:48 MEST 2001

```David Culp wrote:

>    I'm trying to use RRDTool to store and then graph values entered over a
> monthly period.
>   The data is coming from a SQL Database  (mm/yy) .
>
>   I solved an earlier problem with data coming in on a daily basis. After
> reviewing the XML file
>   from RRDtool DUMP, I entered the data as  mm/dd/yy  8:00pm (?), step 86400 ...
> Anyway, that works, but now
>   I'm having trouble with Monthly values.
>   The end result will be a graph of  values each month (just the value, no
> averages ...).
>
>   Any help would be greatly appreciated.

Right.  It may help if you describe your problem ...

I'll give it a try:

Do you have a problem understanding the concept of storing data at
times equal to i*s where i is an arbitrary integer and s is the step
size  (and i*s is the number of seconds since the unix epoch)?

If so: Each interval goes from i*s to i*s+s.  Right now the time is
"Wed Sep  5 01:40:04 MET DST 2001" which is 999646804.  If s is one
day (86400 seconds) then the interval that contains this time will
be the interval from 999561600 to 999648000 (which is the interval
of Sep 4 02:00:00 MET DST 2001 to Sep 5 02:00:00 MET DST 2001.
For these numbers, i will be 11569 and s will be 86400.  The resulting
times (999561600 and 999648000) specify the UTC time in number of
seconds since january 1st, 1970, 00:00:00 without taking into
account leap seconds.

Do you have a problem understanding the concept of step size ?
If so: Each interval will have a fixed duration.  This is also true
when graphing your data.  Each pixel will have a fixed duration.
You cannot, using mrtg nor using rrdtool, have one pixel mean
28 days (february) and the next pixel 31 days.
What you *can* do is store your data per day and plot 28 pixels
for february and 31 pixels for march.  Each day will, of course,
be the UTC day (see previous

If this doesn't help you, describe your problem in stead of just
saying that you have a problem.  Do so to the list, not to me.

HTH
--
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