[rrd-users] 3 questions

[Simon Hobson]

Shabnam Shahreza wrote:

>1)      How can I draw only dots/pixels for the VDEF (MAXIMUM) 
>values and not *line* or dashed line?
>I mean only one dot for the maximum value for start-to-end time period?

Dunno, sorry

>2)      And how can I compare different VDEF (MAXIMUMs) from several 
>rrd files in one graph and pick the MAX of them? Do I need to create 
>a new rrd file and extract the max from there?

You can access multiple RRD files in one graph like this :
DEF:a=rrdfile1.rrd:x:MAX
DEF:b=rrdfile2.rrd:x:MAX

Then you can use the RPN stuff to select the max, like this :
CDEF:abmax=a,b,GT,a,b,IF
a,b,GT puts a result on teh stack to say if it's true or not, then 
(something),a,b,IF selects a if (something) is true or b if it's not. 
The result is if a>b then select a, else select b.

Of course, the simpler way I'd overlooked is just :
CDEF:abmax=a,b,MAX

>3)      And how can I calculate separate VDEF (MAXIMUM) for 
>different start-to-end time frames in one graph, such as monthly?

You can add time spans to a DEF statement :
DEF:c=rrdfile1.rrd:x:MAX:step=(something):start=(something):end=(something)
VDEF:cmax=c,MAXIMUM


See
http://oss.oetiker.ch/rrdtool/doc/rrdgraph_rpn.en.html

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Simon Hobson

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