[rrd-users] Autoscaling y-axis max and min to same absolute value

Simon Hobson linux at thehobsons.co.uk
Wed Oct 8 20:39:50 CEST 2008

Tobias Oetiker wrote:

>  > I've got several traffic graphs that map inbound traffic to positive
>>  y-values and outbound traffic to negative y-values. I want the y-axis
>>  to continue autoscaling, but I would like the max and min values to
>>  scale at the same rate. In other words, abs(min) should always equal
>>  abs(max). Is this possible with rrdgraph?
>you could paint outbund traffic with the background color in the
>positive y axis and the other way round, then the graph will scale

I had to think about that for a minute, it might not be clear to a new user.

Just to clarify, you mean :

Paint outbound traffic as positive using background colour
Paint inbound traffic as positive with inbound data colour

Paint inbound traffic as negative using background colour
Paint outbound traffic as negative using outbound data colour

Thus the Y axis will scale on the positive side to include the max 
value of inbound or outbound traffic, and it will scale on the 
negative side to include the min value of -ve inbound and -ve 
outbound traffic. Painting the data with the background colour 
doesn't draw anything visible, but it will cause the graph to 
autoscale to include it.

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