histogram with negativ values

[Christian-72]

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. I would also expect this for
the stacked histogram. But gnuplot does not work this way.

Is this a bug? Will this be changed in the future.



I could do a multiplot as workarround but I'm not very happy with the
solution.

Thanks
Christian


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[Ethan Merritt]

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.

> But gnuplot does not work this way.
>
> Is this a bug? Will this be changed in the future.

No bug that I know of.
If you have a script that mis-behaves, please provide the script.

--
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742

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[Christian-72]

>From: "Ethan Merritt" <merritt@...>
> 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. I think plotting
negativ values stacked on the negative axis makes more sense than
subtracting the negative value from the stacked bar. This makes the plot
senseless for me.

Cheers
Christian


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[Ethan Merritt]

On Wednesday 09 July 2008 15:16:03 Christian wrote:

>
> >From: "Ethan Merritt" <merritt@...>
> > 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

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