Re: histogram with negativ values

[Ethan M. <merritt@u.washington.edu>]

On Wednesday 09 July 2008 15:16:03 Christian wrote:
> 
> >From: "Ethan Merritt" <merritt@u.washington.edu>
> > On Wednesday 09 July 2008 02:58:05 Christian wrote:
> >> Hello,
> >>
> >> I tried the histogram function with gnuplot. I have positive and negative
> >> values. I would expect that negative values will be start from zero but 
> >> in
> >> the opposite direction as the positive values.
> >
> > They do, yes.
> >    set style plot histogram cluster
> >    set auto y
> >    plot 'foo' (column(1)), 'foo' (-column(1))
> > gives you one bar going up and one bar going down for each entry.
> 
> >> I would also expect this for  the stacked histogram.
> >
> > That would make no sense. It is not possible to mix positive and negative
> > values in a  stacked histogram.  The resulting represenation has no
> > unique interpretation.  In a nutshell, the plot would be useless.
> 
> It would make sense in some cases. For example I have 4 values e.g. a, b, c 
> and d which change over the time. The values c and d are negativ and it 
> should a + b = c + d. So I would like to plot all in a stacked histogram a 
> and b on the positive side and c + d on the negativ. 

Ah, I see. 
That would be a special case of a "back-to-back" or "violin" plot, one where
you have pre-modified the data so that one subset is always positive
and a different subset is always negative.

I think it is possible to do that in a single plot by filtering the data as you
go, but I'd have to play around with the scripting.   I guess this is what you
meant when you said there was an option to use multiplot.   Now I understand,
but I think you can probably accomplish this without using the "multiplot"
command.

-- 
Ethan A Merritt