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Re: Examples of use of svg.el?

From: Eduardo Ochs
Subject: Re: Examples of use of svg.el?
Date: Fri, 1 Apr 2022 21:12:38 -0300

On Fri, 1 Apr 2022 at 18:47, Michael Heerdegen <> wrote:
> Eduardo Ochs <> writes:
> > Hi list,
> >
> > I am trying to learn how to use svg.el, and I plan to use it mainly to
> > plot mathematical functions.
> Why don't you want to use Calc?
> Michael.

Hi Michael,

I don't have a short answer for that, but I'll try to make my longish
answer short enough...

There are some programs that most people find very easy and a few
people find very hard. My favorite example of that is Org, see:

A quote:

  "At some point in 2021 I finally understood why I have always found
  Org Mode so hard to use. To make a long story short, I am a very bad
  _user_: when I try to use something and I can't make a clear mental
  model of what's going on my first reaction is to try to look at the
  data structures and at the source code - and the code that
  implements code blocks in Org is hard to understand."

I was never able to learn Calc properly, and I _guess_ that the main
reason for that is because I've never found a good way to record my
interactions with Calc and "play them back" later.

Take a look at the first three screenshots in:

The third screenshot shows a quadratic function. I know how to make
Maxima draw something very similar to that; Maxima generates a script
for gnuplot, and asks gnuplot to render it. The script can be saved to
a file, and I learned a lot about gnuplot by examining these scripts.

I only learned that Calc can do graphics via gnuplot a few minutes

  (info "(calc)Graphics")

The quadratic function in my third screenshot is defined in this way:

  x0 = 3
  y0 = 2
  z = z(x,y) = (x-x0)^2 - (y-y0)^2 + 2

How would you make Calc plot it for x in [x0-1,x0+1] and y in
[y0-1,y0+1]? Also: how do we access the script that Calc sends to

Btw, my way to script my interactions with Maxima is demo-ed here:

The third thumbnail - the one that shows a 3D plot - points to this,

that nowadays is one of my favorite short demos of eev in action - as
in: "hey, if you've never seen how to use eev to control REPLs then
follow this link and watch 30 seconds of the video... note that the
`&t=15m14s' make Youtube start playing it from 15:14".

I would _really_ love to make something similar for Calc. Any help
would be greatly appreciated!

  Cheers & thanks in advance,
  Eduardo Ochs

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