# [rrd-users] R: Re: RRD - Working with unknow data and changing unknown into zero

Simone Felici s.felici at alpikom.it
Tue Feb 3 23:21:15 MET 2004

```Thank you for your answer Alex!

It's all ok about the question on how resolve some peaks on the graph,
expect for the "restore_with_some_flag", but no problem, I'll try to
dump, edit and then restore! :)

For my first question (the most important) I haven't understood very
well.
Let me see if I've understood well the docs U've written about the
unknown values :P
If I've to sum two (or more) values into one variable, if ONLY one of
these is unknown, also the result of the sum is unknown too, also I've
to check the unknown values and convert into zero to make the sum right.

Ok, If the above is right I must do this to see any graph.

Other think I haven't understood is WHY the MAX and AVERAGE values are
right and the MIN and LAST not?
Example, if I've 3 intervals SUM1 = 3 + 5 = 8, SUM2 = 2 + 3 = 5, SUM3 =
1 + 1 = 2

I should have MAX = 8, MIN = 2, AVERAGE = 5, LAST = 2; but I receive MAX
= 8, MIN = 0, AVERAGE = 5 and LAST = 0.
I think it's strange, the values should be calculated on the different
sums... And it happens ONLY If I convert unknown values into zero (to
obtain a graph, otherwise no graph is shown if there are NaN values)

Ok, maybe I'm wrong, any help? :)

Thank's a lot to everyone!

Simon

-----Messaggio originale-----
Da: rrd-users-bounce at list.ee.ethz.ch
[mailto:rrd-users-bounce at list.ee.ethz.ch] Per conto di Alex van den
Bogaerdt
Inviato: martedì 3 febbraio 2004 18.02
A: rrd-users at list.ee.ethz.ch
Oggetto: [rrd-users] Re: RRD - Working with unknow data and changing
unknown into zero

On Tue, Feb 03, 2004 at 05:23:54PM +0100, Simone Felici - Alpikom Spa
wrote:

> Reading the CDEF tutoria I've found the syntax to convert unknown
> values into zero but after this operation the LAST and MIN values are
> ZERO too...

> Questions:
>
> 1- Any Idea why?

Sure.  You _have_ actually changed the values so the minimum, if not
below zero, the minimum is actually becoming zero.

How to circumvent is your next question:  Answer is to make a copy, use
one copy to determine min,avg,max etc. and the other copy to alter
unknown in zero.

> 2- Other thing. In some cases I receive some peaks on graphs. Can I
> edit the rrd file manually and delete the wrong values? (Or any other
> solution...)

1: dump, edit, restore.
2: dump, restore_with_some_flag

HTH,
Alex
--

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