Re: Taylor expansion does not expand well

[Nicholas Jankowski]

On Thu, Dec 10, 2015 at 12:05 PM, Andy Buckle <address@hidden> wrote:

On 10 December 2015 at 16:56, Jonathan Camilleri <address@hidden> wrote:

How does this work please?

f=[1,3,3]
f =

   1   3   3

octave:2> g = taylor(1,'expansionPoint',1,'order',4)

Error: 
error: 'taylor' undefined near line 1 column 5

What does this error mean please?

I am using http://octave-online.net/.

See post at http://math.stackexchange.com/questions/209320/where-do-the-factorials-come-from-in-the-taylor-series.

See https://en.wikipedia.org/wiki/Taylor_series.

Documentation at http://octave.sourceforge.net/symbolic/function/@sym/taylor.html would be helpful if it included more clear examples, preferably ones which are complete.

You may use data sets to include tutorials if you wish, as I fail to see a complete implementation in place.

"'taylor' undefined" means it can't find the function, taylor. Do you have the symbolic package installed and loaded?

If you do 

pkg list

do you see a star next to symbolic?

--

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I just checked out octave-online.net, and symbolic 2.1.0 should be installed and loaded by default. (list below).  I'm running a newer version (2,2,2). Jon, it is part of the symbolic package, and for it to work you have to call it with symbolically declared variables.  (try: help sym)

Depending on how I try to call taylor, I get the same response. I'm not sure what the expected behavior is:

>> a = sym('a')
a = (sym) a

taylor(a)
a = (sym) a

>> taylor(sin(a))
ans = (sym)

    5    3
   a    a
  --- - -- + a
  120   6

Alll good.

now, calling with a nonsymbolically defined argument:

>> b = [1:10];
>> taylor(sin(b))
error: 'taylor' undefined near line 1 column 1

Seems like it should give a better answer than that, as this seems like it can't find taylor, when it's just called incorrectly. does that have something to do with how the interpreter looks for the package function?

What's more, trying the same on octave-online.net:

octave:10> a=sym ('a')
a = (sym) a

octave:11> taylor(a)
error: structure has no member '
'
error: called from:
error:   /usr/local/share/octave/packages/symbolic-2.1.0/@sym/symvar.m at line 98, column 14
error:   /usr/local/share/octave/packages/symbolic-2.1.0/@sym/taylor.m at line 46, column 7

Is this just a 2.1.0 bug?

octave:2> pkg list

 Package Name         | Version | Installation directory
---------------------+---------+-----------------------
     communications *|   1.2.0 | .../share/octave/packages/communications-1.2.0
            control *|   2.6.6 | /usr/local/share/octave/packages/control-2.6.6
       econometrics *|   1.1.1 | .../share/octave/packages/econometrics-1.1.1
          financial *|   0.4.0 | .../local/share/octave/packages/financial-0.4.0
fuzzy-logic-toolkit *|   0.4.4 | .../octave/packages/fuzzy-logic-toolkit-0.4.4
            general *|   1.3.4 | /usr/local/share/octave/packages/general-1.3.4
           geometry *|   1.7.0 | /usr/local/share/octave/packages/geometry-1.7.0
                 io *|   2.2.7 | /usr/local/share/octave/packages/io-2.2.7
     linear-algebra *|   2.2.1 | .../share/octave/packages/linear-algebra-2.2.1
          mechanics *|   1.3.1 | .../local/share/octave/packages/mechanics-1.3.1
      miscellaneous *|   1.2.1 | .../share/octave/packages/miscellaneous-1.2.1
                nan  |   2.7.1 | /usr/local/share/octave/packages/nan-2.7.1
             odepkg *|   0.8.4 | /usr/local/share/octave/packages/odepkg-0.8.4
              optim *|   1.4.1 | /usr/local/share/octave/packages/optim-1.4.1
        optiminterp *|   0.3.4 | .../share/octave/packages/optiminterp-0.3.4
           parallel *|   2.2.0 | /usr/local/share/octave/packages/parallel-2.2.0
             signal *|   1.3.0 | /usr/local/share/octave/packages/signal-1.3.0
            splines *|   1.2.7 | /usr/local/share/octave/packages/splines-1.2.7
         statistics *|   1.2.4 | .../share/octave/packages/statistics-1.2.4
            strings *|   1.1.0 | /usr/local/share/octave/packages/strings-1.1.0
             struct *|  1.0.10 | /usr/local/share/octave/packages/struct-1.0.10
           symbolic *|   2.1.0 | /usr/local/share/octave/packages/symbolic-2.1.0