gnuplot-info

[Gnuplot-info] question on "parametric" data style

[Dr. I. D. J. <die...@t-...>]

Dear listmembers,
I have a function (polar diagram) covering many decades of values. I would 
like to have a constant number of values per decade rather than one with 
constant spacing (configured via "set samples VALUE")

I helped myself by creating a file "sourcefile" containing a correspondingly 
configured set of values and using those for my plot.

I. e. I have two functions RE(x) and IM(x), and rather than performing a

set parametric
set trange [0.01:1000000]
plot RE(t),IM(t)

I did a

plot "sourcefile" using RE($1):IM($1)

where "sourcefile" contains a set of values like

0.01,0.02 ...0.1,0.2, say 10 per decade.

This works fine for me but seems somewhat much effort. Is there a more 
"intelligent" way to tell gnuplot to use I. e. a constant number of values per 
decade in parametric mode? Otherwise I have to increase the number of samples 
(nearly ..) beyond all bounds what increases the computation time drastically.

I could not find a corresponding hint neither in "help set samples" nor in 
"help set parametric"

Thank you very much for your efforts,
take care




Dieter Jurzitza

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Re: [Gnuplot-info] question on "parametric" data style

[Hans-Bernhard B. <HBB...@t-...>]

On 03.10.2011 10:42, Dr. Ing. Dieter Jurzitza wrote:

> I have a function (polar diagram) covering many decades of values. I would
> like to have a constant number of values per decade rather than one with
> constant spacing (configured via "set samples VALUE")

So what you're trying to do is, essentially, a log-scaled 't' axis. 
Unfortunately, gnuplot doesn't do that by itself.  It accepts the 
command "set log t", but doesn't do anything with it.

But read on.

> I. e. I have two functions RE(x) and IM(x), and rather than performing a
>
> set parametric
> set trange [0.01:1000000]
> plot RE(t),IM(t)

Just transform 't' as you go:

set trange [-2, 6]
plot RE(10.0**t), IM(10.0**t)

Re: [Gnuplot-info] question on

[Thomas S. <t.s...@fz...>]

Dr. Ing. Dieter Jurzitza <dieter.jurzitza <at> t-online.de> writes:

> ...
> I have a function (polar diagram) covering many decades of values. I would 
> like to have a constant number of values per decade rather than one with 
> constant spacing (configured via "set samples VALUE")
> ...
> set parametric
> set trange [0.01:1000000]
> plot RE(t),IM(t)
> ...

you may transfer a linear trange into an exponential one via '10**t':

set trange [-2:6]
set samples 81
plot RE(10**t),IM(10**t)