[rrd-users] AREA starting at value rather than at y=0

[Alex van den Bogaerdt]

On Thu, Oct 04, 2007 at 02:35:16PM -0700, Joseph Mack NA3T wrote:
> using rrdtool-1.0.45
> 
> I have a value with a +/- error margin . I'd like to have an 
> AREA starting at (value-error) of height 2*error to give a 
> band of color corresponding to the error limits.
> 
> I've tried starting the bottom with AREA:(value-error) using 
> black or white as the color of AREA, but these colors are 
> obtrusive. I'd rather have a transparent AREA. (I then STACK 
> 2*error.) Alternately I use LINE2 for the lower limit, the 
> most likely value, and the upper limit, but then there are 3 
> lines and the viewer thinks I'm plotting 3 values.
> 
> Any suggestions?

Keep it as is, except that you change the color from black or
white into fully transparent.

You can do this by leaving out the color, or by explicitly setting
transparency to full:


LINE1:valueminuserror
AREA:errortwice#FF0000:errorrange:STACK

or

AREA:valueminuserror#12345600:legend
AREA:errortwice#FF0000:errorrange:STACK

or

AREA:valueminuserror#1230:legend
AREA:errortwice#F00:errorrange:STACK

-- 
Alex van den Bogaerdt
http://www.vandenbogaerdt.nl/rrdtool/