On Oct 19, 2016 6:00 AM, <rrd-users-requ...@lists.oetiker.ch> wrote:
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Re: Confusion about VDEF total and graph values (humke) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Mon, 17 Oct 2016 20:25:37 +0200 > From: Christian Garbs <mi...@cgarbs.de> > To: Alex van den Bogaerdt <a...@vandenbogaerdt.nl> > Subject: Re: [rrd-users] rrdgraph: Negative values with --logarithmic > Message-ID: <20161017182537.ga30...@cgarbs.de> > Content-Type: text/plain; charset=utf-8 > > On Mon, Oct 17, 2016 at 03:01:11AM +0200, Alex van den Bogaerdt wrote: > > > 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... > > Basically, yes, but because of the y axis I think I need some special > logic in rrdgraph (see below). > > > > 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 ? > > This would indeed give me the correct results and would draw a correct > graph, but the y axis grid would not be logarithmic: > > If I put the values "1000" and "-1000" into a CDEF using normal and > 'mirrored' LOG, I'll graph the values "3" and "-3". The y grid will > propably autoscale to "-10 ? 10" and show my values as "3" and "-3" > instead of "1000" and "-1000". > > When I use --logarithmic, the positive values are also LOGed, but the y > axis will be scaled logarithmic as well, so the y axis will show > "1000" (or "10e3" or "1k") next to the graph value. > > If I could get a logarithmic y axis without using --logarithmic (for > both positive and negative values), using LOG in a CDEF would indeed > be a solution. > > Regards > Christian > -- > ....Christian.Garbs....................................https > ://www.cgarbs.de > > "Die Ber?hmtheit mancher Zeitgenossen h?ngt mit der Bl?dheit > der Bewunderer zusammen." -- Heiner Geissler > > > > ------------------------------ > > Message: 2 > Date: Wed, 19 Oct 2016 00:44:54 -0700 (MST) > From: humke <arjan.hum...@gmail.com> > To: rrd-users@lists.oetiker.ch > Subject: Re: [rrd-users] Confusion about VDEF total and graph values > Message-ID: <1476863094342-7583447.p...@n2.nabble.com> > Content-Type: text/plain; charset=us-ascii > > Alex van den Bogaerdt-5 wrote > >> Alex van den Bogaerdt-5 wrote > >>> You mean you want to see the same bars, only reduced in width? In other > >>> words, get smaller bars with gaps inbetween? > >> > >> That would also work visually, but what I had in mind was not to reduce > >> the > >> width, but create the bars by separating them with vertical lines of the > >> correct height. > > > > I have difficulty understanding what you describe here. > > This piece of paint art shows best what I mean. Just smaller bars as per > your suggestion would also work. I understand we will still be showing > rates, but if the graph visually looks different (more like a histogram) > when we CDEF'd a rate, that would be a nice visual cue that we did > something > to the original data (* 3600 in my case). Of course, title and comment > strings could also be used to inform the viewer. > > <http://rrd-mailinglists.937164.n2.nabble.com/file/ > n7583447/gas_withlines.gif> > > Arjan > > > > > -- > View this message in context: http://rrd-mailinglists. > 937164.n2.nabble.com/Confusion-about-VDEF-total-and-graph-values- > tp7583425p7583447.html > Sent from the RRDtool Users Mailinglist mailing list archive at Nabble.com. > > > > ------------------------------ > > Message: 3 > Date: Wed, 19 Oct 2016 00:54:29 -0700 (MST) > From: humke <arjan.hum...@gmail.com> > To: rrd-users@lists.oetiker.ch > Subject: Re: [rrd-users] Confusion about VDEF total and graph values > Message-ID: <1476863669285-7583448.p...@n2.nabble.com> > Content-Type: text/plain; charset=us-ascii > > Simon Hobson-2 wrote > > I interpret him as : think about drawing each column in the graph as a > box > > with a thin (I guess 1 pixel is the minimum) outline round it in a > > contrasting colour - but don't draw the top or bottom lines. You've now > > got vertical lines separating the filled area. > > > > It's slightly more subtle, you actually want to only draw a line on > either > > the right, or the left, of each column - otherwise the side lines from > two > > adjacent columns combine to form a 2 pixel wide line. > > > > It also won't work if the columns are only 1 pixel wide. > > Almost... See my other post of today for a picture of what I mean. > > RRDgraph allows us to draw with pixels < 1 in size (I actually use 0.8 in > my > graphs). There's no such thing as half (or <1) a pixel in reality, but the > rendering process uses the number to do some special 'smoothing' (there's a > better term that won't pop up in my head) to make it visually look like a > thinner line. I am not sure if it would help to give the desired effect in > this case. If we could even generate the vertical lines that is which I so > much desire ;) > > > > > > -- > View this message in context: http://rrd-mailinglists. > 937164.n2.nabble.com/Confusion-about-VDEF-total-and-graph-values- > tp7583425p7583448.html > Sent from the RRDtool Users Mailinglist mailing list archive at Nabble.com. > > > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > rrd-users mailing list > rrd-users@lists.oetiker.ch > https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users > > > ------------------------------ > > End of rrd-users Digest, Vol 118, Issue 6 > ***************************************** >
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