I thought I would try this in ChatGPT since one of the answers sounded
gpt-ish. Quite surprised by the results in terms of level of detail about
what is going on in the routine that it presented. I marked the line that
was needed to make the function of the gpt-answer work:
def printSeries(expIn):
expOut = expIn
expOut = collect(expOut, t)
expList = expOut.as_ordered_terms() # convert expression to list
expList = [i.as_coeff_Mul() for i in expList] # <---- needed this line
expList = [(t, round(coeff, 5)) for coeff, t in expList] # round
coefficients to 5 digits
expList.sort(key=lambda term: term[0].as_poly().degree(),
reverse=True) # sort terms by degree of t
expStr = ' '.join([f"{coeff:.5g} {t}" for t, coeff in expList]) #
format terms as strings
print(expStr)
/c
On Monday, March 6, 2023 at 10:45:51 AM UTC-6 Oscar wrote:
> The degree function can be imported like
>
> from sympy import degree
>
> It is used to get the degree of a polynomial expression.
>
> On Mon, 6 Mar 2023 at 14:53, Thomas Ligon <thomas...@gmail.com> wrote:
> >
> > Thanks! That's a big help, but I am not finished yet. Here is where I am
> now:
> >
> > Step 1: Use your code.
> > name 'StrPrinter' is not defined
> > changed StrPrinter to sympy.printing.str.StrPrinter
> > https://docs.sympy.org/latest/modules/printing.html
> > name 'degree' is not defined
> > I tried key=sympy.printing.str.degree, but that gave me
> > module 'sympy.printing.str' has no attribute 'degree'
> > Then I tried key=sympy.degree and that worked.
> > Now the two series are being printed in the desired order.
> >
> > Step 2: Use latex
> > I tried changing print(doprint(series)) to print(latex(doprint(series)))
> > and the result is
> > \mathtt{\text{-2.565*t + 147.94*t**3 - 2867.7*t**5}}
> > which doesn't format correctly in Word's equation editor or in
> www.overleaf.com,
> > where it formats correctly, but issues an error
> > Undefined control sequence.
> > LaTeX Error: \mathtt allowed only in math mode.
> > I tried changing the string to
> > -2.565*t + 147.94*t**3 - 2867.7*t**5
> > and this formats correctly in Word and in Overleaf.
> > Then I tried
> > doprint =
> sympy.printing.latex.LatexPrinter(settings={'order':'none'}).doprint
> > but that throws an exception
> > '_PrintFunction' object has no attribute 'LatexPrinter'
> > even though the class
> > class sympy.printing.latex.LatexPrinter(settings=None)
> > is defined in
> >
> https://docs.sympy.org/latest/modules/printing.html#module-sympy.printing.latex
> >
> > Still to do:
> > Learn how this works.
> > Learn why evalf(5) works. The documentation at
> > https://docs.sympy.org/latest/modules/evalf.html
> > doesn't make it clear to me what the possible arguments are and what
> they mean.
> > Find documentation for sorted and key=degree.
> > I searched for sympy degree and found polynomials and angles, but still
> don't understand this one.
> >
> >
> > On Sunday, March 5, 2023 at 8:53:32 PM UTC+1 Oscar wrote:
> >
> > On Sun, 5 Mar 2023 at 08:32, Thomas Ligon <thomas...@gmail.com> wrote:
> > >
> > > I have a lot of power series that look like this (but going up to
> t**12):
> > > exp1 = -2867.70035529489*t**5 + 147.938724526848*t**3 -
> 2.56500070531002*t
> > > While trying to gain some insight into the mathematics that creates
> them, I want to print a shorter version, such as
> > > - 2.565 t + 147.93872 t**3- 2867.70036 t**5
> > > but the best I have achieved is
> > > - 2867.70036 t^{5} + \left(147.93872 t^{3} - 2.565 t\right)
> > > Rounding the numbers was easy, but I would prefer to round to 5 digits
> total, not 5 digits after the decimal point. I was able to convert the
> expression to a list and sort the list, but when I converted the list back
> to an expression, I didn't succeed in producing the order I wanted.
> >
> > You can get 5 digits by using exp1.evalf(5).
> >
> > It is surprisingly difficult to control the order of terms in sympy's
> > printing functionality but it is possible:
> >
> > In [1]: exp1 = -2867.70035529489*t**5 + 147.938724526848*t**3 -
> > 2.56500070531002*t
> >
> > In [2]: doprint = StrPrinter(settings={'order':'none'}).doprint
> >
> > In [3]: series = Add(*sorted(exp1.evalf(5).args, key=degree),
> evaluate=False)
> >
> > In [4]: print(doprint(series))
> > -2.565*t + 147.94*t**3 - 2867.7*t**5
> >
> > There are two steps to controlling the order:
> >
> > - Ordering the terms in the expression itself (the series variable
> above).
> > - Getting the printer to respect that ordering ('order':'none').
> >
> > It should be possible to set order=None with init_printing and that
> > does work for the pretty printer but not for string printing (i.e.
> > print(expr) or str(expr)).
> >
> > --
> > Oscar
> >
> > --
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> Groups "sympy" group.
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> .
>
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