gnuplot-info — For questions and discussion about gnuplot

Re: [Gnuplot-info] invalid context

[theozh <th...@gm...>]

What is the larger context of your script snippet?

What should happen if flag_satur!=0 ?
Then $EXT_CEN should become (or stay) undefined or become something else?

> Hello,
>
> It seems that I cannot do this
> if (flag_satur==1) {
> $EXT_CEN << EOD
>   0.0 1e10 1e-13
>   0.0 1e10 1
>   EOD
> }
>

Re: [Gnuplot-info] awk

[theozh <th...@gm...>]

and what about something like this?

FILE = "population.dat"
cmd  = sprintf("< awk -f ~/awk/read_profiles.awk -v coly=5 %s", FILE)
plot cmd u 1:2

[Gnuplot-info] invalid context

[Patrick D. <pd...@gm...>]

Hello,

It seems that I cannot do this
if (flag_satur==1) {
$EXT_CEN << EOD
 0.0 1e10 1e-13
 0.0 1e10 1
 EOD
}

I get
attempt to define data block from invalid context

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================

Re: [Gnuplot-info] awk

[Patrick D. <pd...@gm...>]

Thank.

But negative.
I used
"< awk -f ~/awk/read_profiles.awk -v coly=5 " . FILE

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================


> Sent: Tuesday, December 06, 2022 at 11:00 AM
> From: "theozh" <th...@gm...>
> To: gnu...@li...
> Subject: Re: [Gnuplot-info] awk
>
> Is there a specific reason, why you think you need awk?
> 
> What about?
> 
> FILE = "population.dat"
> set datafile separator comma
> plot FILE ($1-1965):2, pop(x)
> 
> best, Theo.
> 
> 
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via: https://lists.sourceforge.net/lists/listinfo/gnuplot-info
>

Re: [Gnuplot-info] awk

[theozh <th...@gm...>]

Is there a specific reason, why you think you need awk?

What about?

FILE = "population.dat"
set datafile separator comma
plot FILE ($1-1965):2, pop(x)

best, Theo.

[Gnuplot-info] awk

[Patrick D. <pd...@gm...>]

Hello,

I would like to do as in the example

plot "< awk ’{print $1-1965, $2}’ population.dat", pop(x)

but with population.dat in a variable.

I did not find the way to do it.
Can somebody put me on the way?

Thank.

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================

Re: [Gnuplot-info] Plotting glucose levels for diabetes

[Norwid B. <nb...@ya...>]

Dear Dave,

back on [2021-11-21 Mon], you wrote to the user list seeking options to
monitor the level of glucose over multiple weeks.[1]

Though I do not know your familiarity with Emacs (both in terms of the editor,
as well as the ecosystem around it), nor orgmode[2], yesterday's presentation
«Health data journaling and visualization with Org Mode and gnuplot» by David
O'Toole equally dealt with monitoring similar data.  So I speculate it might
be of interest for you, or other subscribers to the list.

This approach includes a simplified input into a template, joining e.g., data
worth a month into a table, and generation of a diagram David demonstrated on
the ongoing EmacsConf 2022.[3]  His talk is available as a transcript,[4] and
as a video recording on youtube[5] of about 25 min.  David shares his template
(permissive MIT license) used on GitLab[6] for additional adjustments.

So far, the benefits extend beyond a monthly map David may share with his GP.
His diagram equally includes user-defined limits, these ease to spot the good
days in one category, or an other (e.g., at least x min of physical exercise,
no more than y tablets); then, the good days are quickly identified as are
possible correlations between the parameters seen, too.

With regards,

Norwid


[1] https://sourceforge.net/p/gnuplot/mailman/message/37388777/
[2] https://orgmode.org/
[3] https://emacsconf.org/2022/
[4] https://emacsconf.org/2022/talks/health/
[5] https://www.youtube.com/watch?v=YmQ1CYMz-OY
[6] https://gitlab.com/dto/health-template

Re: [Gnuplot-info] Possible optimal way to handle extremum points problem

[Ethan M. <eam...@gm...>]

On Tuesday, 29 November 2022 21:17:18 PST Nikita Zlobin via gnuplot-info wrote:

I like the idea.  

The program already does something of the sort to insure that a function
is evaluated at x=0 even if regular subdivision of the x-axis range would
not generate a sample point there.  If the location of the function's
extrema are known in advance, those special values of x could be added
to the sample set.  Unfortunately the program does not in general know
how many or where such extrema are expected.

On the other hand, for periodic functions such as the example you show there
is another option.  Set the sampling range to span exactly one period and
plot as many periods as needed to fill the desired x range.

For your function   abs(sqrt(sin(x)))

    unset key
    set sample 99   # odd number advised
    set xrange [-8:8]
    f(x) = abs(sqrt(sin(x)))
    offset(i) = t + i * 2*pi
    plot for [i=-2:2] [t=0:2*pi] '+' using (offset(i)):(f(offset(i))) lt 1

99 samples is sufficient to give a reasonably smooth plot;
199 samples is even better.


	Ethan


> I tried to plot «sqrt( sin(x) )» and noticed, that at 1000 samples with xrange [-8:8] lines break at visible distance from X axis. Even 10000 samples is not enough, and only 100k or 1m samples is more or less fine. Of course, it’s not good for vector documents like svg, eps or whatever latex terminals generate.
>  
> This problem of open ends could solved by adding point between existing and non-existing neighbor points and adjusting its place with subdivide and conquer approach.
>  
> Ideally this point could use one of reserved position for non-existing point, thus reducing chance of points number growth.
>  
> Also, if points number growth is not problem, there could be second threshold to use for middle subdivisions, just to keep visually good resolution. This would allow to use minimum necessary points in the best way. In case if threshold for middle subdivisions is not specified, it could be calculated horizontal distance (may be multiplied by 2).
>  
> --
> Nikita Zlobin

[Gnuplot-info] Possible optimal way to handle extremum points problem

[Nikita Z. <coo...@ma...>]

I tried to plot «sqrt( sin(x) )» and noticed, that at 1000 samples with xrange [-8:8] lines break at visible distance from X axis. Even 10000 samples is not enough, and only 100k or 1m samples is more or less fine. Of course, it’s not good for vector documents like svg, eps or whatever latex terminals generate.
 
This problem of open ends could solved by adding point between existing and non-existing neighbor points and adjusting its place with subdivide and conquer approach.
 
Ideally this point could use one of reserved position for non-existing point, thus reducing chance of points number growth.
 
Also, if points number growth is not problem, there could be second threshold to use for middle subdivisions, just to keep visually good resolution. This would allow to use minimum necessary points in the best way. In case if threshold for middle subdivisions is not specified, it could be calculated horizontal distance (may be multiplied by 2).
 
--
Nikita Zlobin

Re: [Gnuplot-info] Shifting Plots on y-axis with units?

[Norwid B. <nb...@ya...>]

On Mon, 21 Nov 2022 11:59:29 -0500
Nicholas Papadonis <nic...@gm...> wrote:

> Does anyone know if gnuplot has the ability to shift plots on the y-axis,
> perhaps keeping association with the units?

@Nicholas

From your description it seems plausible you refer to /stacked plots/.  Have a
look on gnuplot's example gallery, section «page layout», entry «multiplot
layout»

https://gnuplot.sourceforge.net/demo_5.2/layout.html

examples four and five.  If I recall correctly, «Gnuplot in Action» by Philip
Janert (Manning Publications) equally describes the stacking curves for the
simultaneous presentation of multiple time series, in one of the later
chapters.  On occasion, it equally is a valuable technique for the visual
comparison of 2D histograms in a column in common if both plots share the same
over all interval, bin size, etc.  (Of course, you have the distributions
mean, median, kurtosis, skewness, etc. as a numeric tool.)

Regards,

Norwid

[Gnuplot-info] Shifting Plots on y-axis with units?

[Nicholas P. <nic...@gm...>]

Does anyone know if gnuplot has the ability to shift plots on the y-axis,
perhaps keeping association with the units?

For instance, if I have multiple sets of data with the same x-range that
appear to correlate in the graph, with different y-axis ranges (which would
place the individual graphs at much different vertical positions), how can
I shift each data set graph to coincide with the others on the vertical
y-axis?

One could think of an example as having different stock tick symbols and
finding a way to shift each individual's symbol graph on the y-axis so one
can compare the trends/spikes easier.

Thanks

[Gnuplot-info] Specifying histogram types in the plot command

[Peter R. <p.r...@sh...>]

Is it possible to specify the type of histogram (cluster, errorbars, 
rowstacked or columnstacked) together with the gap and box width 
directly in the 'plot' command? (As opposed to issuing things like 'set 
style histogram rowstacked' /before/ the 'plot' command.) I know 
specifying things like 'fill' for the bars is possible. Is there 
something like a "with histogram rowstacked" option for 'plot'?

I ask because experience tells me that this sort of option is possible 
for other, non-histogram plotting styles, but is often not documented. 
(FWIW: I do have a specific reason for wanting to setup things in the 
'plot' command.)

Peter

Re: [Gnuplot-info] sum

[Patrick D. <pd...@gm...>]

Hello,

would it possible to pass the function (here f(x)) as a parameter
or a pointer to the function f(x) ?

Thank

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================


> Sent: Tuesday, November 01, 2022 at 10:35 PM
> From: "theozh" <th...@gm...>
> To: gnu...@li...
> Subject: Re: [Gnuplot-info] sum
>
> maybe something like this...?
> 
> mySum(xmin,xmax,N) = sum[i=0:N-1] (x0=xmin+real(xmax-xmin)/(N-1)*i,f(x0))
> 
> f(x) = x
> print mySum(1,100,100)
> 
> f(x) = x**2
> print mySum(-10,10,2001)
> 
> Results: 5050.0 and 66766.7
> 
> You need real() to avoid gnuplot's integer division.
> Alternatively, you have to ensure that xmin or xmax are floating point numbers.
> 
> Am 01.11.2022 um 20:55 schrieb Patrick Dupre:
> > set samples 2001
> >
> > f(x)= ..
> >
> > I wish to get the sum of f(x) from [-10:10]
> >
> 
> 
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via: https://lists.sourceforge.net/lists/listinfo/gnuplot-info
>

Re: [Gnuplot-info] nan

[Dan H. <dan...@ph...>]

On Tue, 1 Nov 2022, Ethan Merritt wrote:

> I don't have an immediate fix for this in gnuplot.

My Gnuplot was compiled without libcerf support, so I can't test it,
but why not do

myfaddeeva(z) = exp(-z**2.0+log(1.0-erfi(-z)/(-I)))

?

Re: [Gnuplot-info] nan

[Peter R. <p.r...@sh...>]

Ummm.... Would the OP's problem be more elegantly solved with a small 
Python script. Or even using Excel to pre-process the data file? 
(Reinhart & Rogoff notwithstanding...)

Peter

On 02/11/2022 05:02, Ethan Merritt wrote:
> Underflow confirmed.
>
> The Faddeeva function is exp(-z^2) * erfc(-i*z)
>
> Calculation of exp(-z^2) underflows to zero at about z = 27.
> Gnuplot's own exp function knows to ignore the floating point
> exception that is generated and just return zero.
> But the implementation used by the Faddeeva function in libcerf
> doesn't do this. It leaves the ERANGE error active.
>
> I don't have an immediate fix for this in gnuplot.
>
> The libcerf library does provide a separate function
> im_w_of_x(x) that would calculate the imaginary part
> without triggering an underflow, but that only helps if
> the calling program already knows there will be an underflow
> and calls the special case instead of the generic routine.
> Gnuplot doesn't currently know to do this.
>
> 	Ethan
>
>
> On Tuesday, 1 November 2022 18:02:33 PDT Ethan Merritt wrote:
>> On Tuesday, 1 November 2022 14:54:01 PDT Patrick Dupre wrote:
>>> Hello,
>>>
>>> Setting
>>> fcn(x,g,G)=-imag(1/(x+I*g)*faddeeva(x/G)
>>>
>>> plot [-30:30] fcn(x,0.01,1)
>>>
>>> provides
>>> nan from values less than -27.28 and more than 27.28
>>> There is not reason for that
>>> The value are small, but not very small
>>> slightly less than
>>> -0.0007586274478
>>>
>>> Any idea?
>>> Good question.
>>> Something in the cerf library is setting a range error (ERANGE)
>>> "Math result not representable".  Possibly this is due to
>>> underflow of the real component, which we could ignore, but that is
>>> only speculation at this point.  Note the result
>>>    gnuplot> print faddeeva(27.)
>>>    {2.50797207889417e-317, 0.0209102719931009}
>>> which indicates that the real component has reached the smallest
>>> representable IEEE double float value.
>>>
>>> I will investigate further.
>>>
>>> 	Ethan
>>>
>
>
>
>
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via: https://lists.sourceforge.net/lists/listinfo/gnuplot-info

Re: [Gnuplot-info] nan

[Ethan M. <eam...@gm...>]

Underflow confirmed.

The Faddeeva function is exp(-z^2) * erfc(-i*z)

Calculation of exp(-z^2) underflows to zero at about z = 27.
Gnuplot's own exp function knows to ignore the floating point
exception that is generated and just return zero.
But the implementation used by the Faddeeva function in libcerf
doesn't do this. It leaves the ERANGE error active.

I don't have an immediate fix for this in gnuplot.

The libcerf library does provide a separate function
im_w_of_x(x) that would calculate the imaginary part
without triggering an underflow, but that only helps if
the calling program already knows there will be an underflow
and calls the special case instead of the generic routine.
Gnuplot doesn't currently know to do this.

	Ethan


On Tuesday, 1 November 2022 18:02:33 PDT Ethan Merritt wrote:
> On Tuesday, 1 November 2022 14:54:01 PDT Patrick Dupre wrote:
> > Hello,
> > 
> > Setting
> > fcn(x,g,G)=-imag(1/(x+I*g)*faddeeva(x/G)
> > 
> > plot [-30:30] fcn(x,0.01,1)  
> > 
> > provides
> > nan from values less than -27.28 and more than 27.28
> > There is not reason for that
> > The value are small, but not very small
> > slightly less than
> > -0.0007586274478
> > 
> > Any idea?
> 
> Good question.  
> Something in the cerf library is setting a range error (ERANGE)
> "Math result not representable".  Possibly this is due to
> underflow of the real component, which we could ignore, but that is
> only speculation at this point.  Note the result
>   gnuplot> print faddeeva(27.)
>   {2.50797207889417e-317, 0.0209102719931009}
> which indicates that the real component has reached the smallest
> representable IEEE double float value.
> 
> I will investigate further.
> 
> 	Ethan
> 

Re: [Gnuplot-info] nan

[Ethan M. <eam...@gm...>]

On Tuesday, 1 November 2022 14:54:01 PDT Patrick Dupre wrote:
> Hello,
> 
> Setting
> fcn(x,g,G)=-imag(1/(x+I*g)*faddeeva(x/G)
> 
> plot [-30:30] fcn(x,0.01,1)  
> 
> provides
> nan from values less than -27.28 and more than 27.28
> There is not reason for that
> The value are small, but not very small
> slightly less than
> -0.0007586274478
> 
> Any idea?

Good question.  
Something in the cerf library is setting a range error (ERANGE)
"Math result not representable".  Possibly this is due to
underflow of the real component, which we could ignore, but that is
only speculation at this point.  Note the result
  gnuplot> print faddeeva(27.)
  {2.50797207889417e-317, 0.0209102719931009}
which indicates that the real component has reached the smallest
representable IEEE double float value.

I will investigate further.

	Ethan

> 
> Thank
> ===========================================================================
>  Patrick DUPRÉ                                 | | email: pd...@gm...
>  Laboratoire interdisciplinaire Carnot de Bourgogne
>  9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
>  Tel: +33 (0)380395988                    | | Room# D114A
> ===========================================================================
> 
> 
> 
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via: https://lists.sourceforge.net/lists/listinfo/gnuplot-info
> 

[Gnuplot-info] nan

[Patrick D. <pd...@gm...>]

Hello,

Setting
fcn(x,g,G)=-imag(1/(x+I*g)*faddeeva(x/G)

plot [-30:30] fcn(x,0.01,1)  

provides
nan from values less than -27.28 and more than 27.28
There is not reason for that
The value are small, but not very small
slightly less than
-0.0007586274478

Any idea?

Thank
===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================

Re: [Gnuplot-info] sum

[Alan C. <ala...@gm...>]

As summation like for calculus?

On 11/1/22, theozh <th...@gm...> wrote:
> maybe something like this...?
>
> mySum(xmin,xmax,N) = sum[i=0:N-1] (x0=xmin+real(xmax-xmin)/(N-1)*i,f(x0))
>
> f(x) = x
> print mySum(1,100,100)
>
> f(x) = x**2
> print mySum(-10,10,2001)
>
> Results: 5050.0 and 66766.7
>
> You need real() to avoid gnuplot's integer division.
> Alternatively, you have to ensure that xmin or xmax are floating point
> numbers.
>
> Am 01.11.2022 um 20:55 schrieb Patrick Dupre:
>> set samples 2001
>>
>> f(x)= ..
>>
>> I wish to get the sum of f(x) from [-10:10]
>>
>
>
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via:
> https://lists.sourceforge.net/lists/listinfo/gnuplot-info
>


-- 
-------------
Education is contagious.

Re: [Gnuplot-info] sum

[theozh <th...@gm...>]

maybe something like this...?

mySum(xmin,xmax,N) = sum[i=0:N-1] (x0=xmin+real(xmax-xmin)/(N-1)*i,f(x0))

f(x) = x
print mySum(1,100,100)

f(x) = x**2
print mySum(-10,10,2001)

Results: 5050.0 and 66766.7

You need real() to avoid gnuplot's integer division.
Alternatively, you have to ensure that xmin or xmax are floating point numbers.

Am 01.11.2022 um 20:55 schrieb Patrick Dupre:
> set samples 2001
>
> f(x)= ..
>
> I wish to get the sum of f(x) from [-10:10]
>

Re: [Gnuplot-info] sum

[Patrick D. <pd...@gm...>]

set samples 2001

f(x)= ..

I wish to get the sum of f(x) from [-10:10]

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================


> Sent: Tuesday, November 01, 2022 at 8:34 PM
> From: "theozh" <th...@gm...>
> To: gnu...@li...
> Subject: Re: [Gnuplot-info] sum
>
> What is your x-range and x-step? Only integer numbers?
> Can you please give an example?
> Have you checked "help sum"?
> 
> 
> _______________________________________________
> gnuplot-info mailing list
> gnu...@li...
> Membership management via: https://lists.sourceforge.net/lists/listinfo/gnuplot-info
>

Re: [Gnuplot-info] sum

[theozh <th...@gm...>]

What is your x-range and x-step? Only integer numbers?
Can you please give an example?
Have you checked "help sum"?

[Gnuplot-info] sum

[Patrick D. <pd...@gm...>]

Hello,

I have a function f(x)
How can I get the sum of all the values calculated by this function?

Thank.

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================

[Gnuplot-info] x2range splot

[Patrick D. <pd...@gm...>]

Hello,

Can I use x2range with splot ?

Thank

===========================================================================
 Patrick DUPRÉ                                 | | email: pd...@gm...
 Laboratoire interdisciplinaire Carnot de Bourgogne
 9 Avenue Alain Savary, BP 47870, 21078 DIJON Cedex FRANCE
 Tel: +33 (0)380395988                    | | Room# D114A
===========================================================================

[Gnuplot-info] Color legend for lc variable

[Debostuti G. <deb...@gm...>]

Dear Gnuplot Community

I am using the following command to plot my data with a set of variable
colors.

splot "Params.dat" using 3:6:1 with points pointtype 7 pointsize 1 lc
variable linewidth 5

I had two questions regarding this:

1. How do I show a legend on the graph that indicates the value each color
signifies, something like what we get using cbrange and palette?

2. How do I set the colors to particular ones instead of the default colors
specified by lc variable?

Thank you

-- 
Debostuti Ghosh Dastidar
Research Associate
PDB-India