[rrd-users] clarification of graph resolution

Simon Hobson linux at thehobsons.co.uk
Tue May 8 20:30:05 CEST 2007

Spencer Anderson wrote:
>I am trying to pick the best graph size for the data I'm trying to 
>present.  I collect data every minute and would like to show 24 
>hours of data on one graph.  Am I correct in assuming that at the 
>default resolution, 1 data point = 1 pixel, I would need a graph 
>1440 (24 hours * 60 minutes) pixels wide to hold all the data points?


>Also, if I leave the default resolution, and create a "last 24 
>hours" graph that is 600 pixels wide, the data still looks like it 
>is my one minute data points, even thought there is no way they 
>could all fit in a 600 pixel graph.  Is RRD averaging the data 
>points so they fit, or just skipping some so they fit?

It fits the data to the graph - so if for example you have 2 1/2 data 
points/pixel, the first pixel would be (a+b+c/2)/2.5, the next would 
be (c/2+d+e)/2.5, and so on.

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