> What I want to achieve (and what I think those other proponents also > had in mind) is that I essentially have some of my data mirrored at > the x-axis for better readability (don't draw two values on top of > each other). > > For example I plot outgoing packets on my network as a positive values > while I plot the incoming packets via CDEF:output=0,outputx,- as > negative values. So the outgoing rate is shown above the x-axis and > the incoming rate below the x-axis.
So, what you want to show is the outcome of a normal logaritmic function, but mirrored. Instead of a new function... > To tame network spikes somewhat I want to change the graph mode to > logarithmic. This works for the positive values, but the negative > values simply vanish. I just want the same transormation that happens > to the positive values applied 'mirrored' the the negative values. > > Think of something like a "display-logarithm" function defined like > this: > > > double disp_log(double y) > { > if (y == 0) { > return 0; > } else if (y > 0) { > return log(y); > } else { > return -log(-y); > } > } > > > While "-log(-y)" might look weird in a mathematical context I think that > it makes sense in describing "do the same as for positive values, only > in the other direction". ... can't you just use CDEF:mirrored=logresult,-1,* ? Or am I missing something ? _______________________________________________ rrd-users mailing list rrd-users@lists.oetiker.ch https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users