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Mathematics Wolfram Language

How to convert numerical polynomial to string as InputForm?

Cesar Lozada

Posted 2 years ago

Hello everybody, I have this polynom: pp = -0.017405914799331364819 u^3 v + 0.051335637554670000974 u^2 v^2 - 0.039163308298495570843 u v^3 + 0.074308214044552913018 u^3 w + 0.60368896954782411026 u^2 v w - 0.51875755425567358214 u v^2 w - 0.16593638775362567794 v^3 w + 1.0000000000000000000 u^2 w^2 - 0.81786201225836559051 u v w^2 - 0.18098149081617408008 v^2 w^2 + 0.34883578259804006389 u w^3 - 0.34621295716497209349 v w^3 How to convert it to String as InputForm ( multiplication signs are required, no sci notation), i.e. how to get; output = `"-0.017405914799331364819u^3v+0.074308214044552913018u^3w+0.051335637554670000974u^2v^2+0.60368896954782411026u^2vw+1.0000000000000000000u^2w^2-0.039163308298495570843uv^3-0.51875755425567358214uv^2w-0.81786201225836559051uvw^2+0.34883578259804006389uw^3-0.16593638775362567794v^3w-0.18098149081617408008v^2w^2-0.34621295716497209349v*w^3"` output must be plain STRING. Thanks in advance, César Lozada

POSTED BY: Cesar Lozada

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Neil Singer

Neil Singer, AC Kinetics, Inc.

Posted 2 years ago

César, You are correct. It seems to be missing in the documentation. I will report the oversight and link this thread. It should be added to the documentation for ToString[], CForm[], and FortranForm[]. I'm glad it helped. I use this feature regularly when I need to parse expressions or export them for use in C or other languages. Regards, Neil

POSTED BY: Neil Singer

Cesar Lozada

Posted 2 years ago

Thanks, Daniel. Now I know how to skip these annoying extra digits at the end of converted numbers. As expressed in my answer to Neil, documentation does not mention this 3rd parameter in ToString[]. That's why this forum is absolutely necessesary. Thanks again and regards, César Lozada

POSTED BY: Cesar Lozada

Cesar Lozada

Posted 2 years ago

Hi Neil, It works. Thanks. I have checked again the documentation for ToString[] and there is not reference to FortranForm or CForm. ToString[] documentation and examples mention only OutpputForm, StandardFrom, InputForm and TraditionalForm. There is no way I can link ToString[] wirh these other forms to make a conversion. Maybe documentation needs to be improved. Regards, César Lozada

POSTED BY: Cesar Lozada

Neil Singer

Neil Singer, AC Kinetics, Inc.

Posted 2 years ago

Did you want the power function? CForm will give you power() instead of ** or do Daniel's approach.

POSTED BY: Neil Singer

Daniel Lichtblau

Daniel Lichtblau, Wolfram Research

Posted 2 years ago

In[6]:= ToString[pp, InputForm, NumberMarks -> False] Out[6]= "-0.017405914799331364819u^3v + \ 0.051335637554670000974u^2v^2 - 0.039163308298495570843uv^3 + \ 0.074308214044552913018u^3w + 0.60368896954782411026u^2vw - \ 0.51875755425567358214uv^2w - 0.16593638775362567794v^3w + \ 1.u^2w^2 - 0.81786201225836559051uvw^2 - \ 0.18098149081617408008v^2w^2 + 0.34883578259804006389uw^3 - \ 0.34621295716497209349v*w^3"

In[6]:= ToString[pp, InputForm, NumberMarks -> False]

Out[6]= "-0.017405914799331364819*u^3*v + \
0.051335637554670000974*u^2*v^2 - 0.039163308298495570843*u*v^3 + \
0.074308214044552913018*u^3*w + 0.60368896954782411026*u^2*v*w - \
0.51875755425567358214*u*v^2*w - 0.16593638775362567794*v^3*w + \
1.*u^2*w^2 - 0.81786201225836559051*u*v*w^2 - \
0.18098149081617408008*v^2*w^2 + 0.34883578259804006389*u*w^3 - \
0.34621295716497209349*v*w^3"

POSTED BY: Daniel Lichtblau

Neil Singer

Neil Singer, AC Kinetics, Inc.

Posted 2 years ago

...and If you need fewer decimal places: ToString[N[pp, 5], FortranForm]

POSTED BY: Neil Singer

Neil Singer

Neil Singer, AC Kinetics, Inc.

Posted 2 years ago

César, How about ToString[pp, FortranForm] Regards, Neil

POSTED BY: Neil Singer

Cesar Lozada

Posted 2 years ago

I found a way. Just like to know if Mathematica can do it directly: lis1 = CoefficientRules[pp, {u, v, w}] lis2 = Map[{If[#[[2]] > 0, "+", ""] <> ToString[#[[2]]], #[[1]]} &, lis1] lis3 = Map[#[[1]] <> If[#[[2]] === {0,0,0}, "", "*" <> ToString[Times @@ ({u, v, w}^#[[2]]), InputForm]] &, lis2] res = StringJoin @@ lis3 Note: Databases sqlite or mysql do not allow "^" as operator. In this case; pp1 = pp /. X_^Y_ -> POWER[X, Y] res = StringReplace[StringReplace[ ToString[N[pp1], InputForm], {"[" -> "(", "]" -> ")", " " .. -> "" }], ".)" -> ")"] But I don't know how to control the number of decimals here. César Lozada

I found a way. Just like to know if Mathematica can do it directly:

lis1 = CoefficientRules[pp, {u, v, w}]
lis2 = Map[{If[#[[2]] > 0, "+", ""] <> ToString[#[[2]]], #[[1]]} &,  lis1]
lis3 = Map[#[[1]] <> If[#[[2]] === {0,0,0}, "", "*" <> ToString[Times @@ ({u, v, w}^#[[2]]), InputForm]] &, lis2]   
res = StringJoin @@ lis3

Note: Databases sqlite or mysql do not allow "^" as operator. In this case;

pp1 = pp /. X_^Y_ -> POWER[X, Y] 
res = StringReplace[StringReplace[ ToString[N[pp1], InputForm], {"[" -> "(", "]" -> ")", " " .. -> "" }], ".)" -> ")"]

But I don't know how to control the number of decimals here.

César Lozada

POSTED BY: Cesar Lozada

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