Re: Pseudodata for Vector Fields [Patch]

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

On Tuesday 15 January 2008 22:34, Peter Danenberg wrote:
> Direction fields come in handy for first order ODEs; some people have
> expressed frustration that they're not directly supported.*
> 
> The attached patch produces two dimensions of data from the pseudofile
> operator when df_current_plot->plot_style == VECTOR

Please see also the comment attached to the patch tracker.

The functionality added by this patch is nice, but unless I am
missing something it comes at a cost.  Because it traps all cases
of "plot with vector", you can now *only* plot vector fields.
It no longer handles the simpler case of a single stream of vectors.

Can we somehow arrange to keep both capabilities?



> allowing you to do things like:**
> 
>     set isosamples 20
>     set samples 20
>     l = 0.05
>     f(t,y) = 2*y + 4 - t
>     g(c,x) = -7/4. + 1/2.*x + c*exp(2*x)
>     plot [0:2][-4:0] '+' using 1:2:(l):(l*f($1,$2)) \
>          with vectors title "dy/dt - 2y = 4 - t", \
>          g(0,x) title "g(c, t) = -7/4 + 1/2t + ce^2t, c = 0", \
>          g(.1,x), g(.2,x), g(.3,x), g(-.1,x), g(-.2,x), g(-.3,x)
> 
> Here's the sourceforge tracker:
> 
>     http://sourceforge.net/tracker/index.php?func=detail&aid=1872528&group_id=2055&atid=302055
> 
> -----------
> * http://thread.gmane.org/gmane.comp.graphics.gnuplot.devel/5805/focus=5814
> ** http://wikisophia.org/wiki/User:Danenberg#Direction_field
> 

-- 
Ethan A Merritt            Courier Deliveries: 1959 NE Pacific
Dept of Biochemistry
Health Sciences Building
University of Washington - Seattle WA 98195-7742