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Re: importing data from Excel to Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg85723] Re: importing data from Excel to Mathematica
  • From: "Steve Luttrell" <steve at _removemefirst_luttrell.org.uk>
  • Date: Wed, 20 Feb 2008 06:55:43 -0500 (EST)
  • References: <fpe06j$ser$1@smc.vnet.net>

I assume you can import your equation string into Mathematica in the form 
"x1 = A x2 + B y1\ny1 = C y2 - D x1" where \n is the newline character.

In[1]:= s="x1 = A x2 + B y1\ny1 = C y2 - D x1"
Out[1]= x1 = A x2 + B y1
y1 = C y2 - D x1

The aim now is to manipulate this into the correct form for an algebraic 
expression that Mathematica can work with.

Split the above single string into two separate strings.

In[2]:= s2=StringSplit[s,"\n"]
Out[2]= {x1 = A x2 + B y1,y1 = C y2 - D x1}

Replace = (i.e. Set) with == (i.e. Equal) to make the strings have the 
correct Mathematica syntax for equations.

In[3]:= s3=StringReplace[s2,"="->"=="]
Out[3]= {x1 == A x2 + B y1,y1 == C y2 - D x1}

Convert the strings to algebraic expressions that Mathematica can manipulate 
symbolically.

In[4]:= e=ToExpression[s3]
Out[4]= {x1==A x2+B y1,y1==-D x1+C y2}

Solve the equations.

In[5]:= Solve[e,{x1,y1}]
Out[5]= {{x1->-((-A x2-B C y2)/(1+B D)),y1->-((A D x2-C y2)/(1+B D))}}

Stephen Luttrell
West Malvern. UK

"Tugrul Temel" <temelt at xs4all.nl> wrote in message 
news:fpe06j$ser$1 at smc.vnet.net...
> Dear All,
>
> I have an Excel database with strings of equations in the following form:
>
> x1 = A x2 + B y1
> y1 = C y2 - D x1
>
> I like to import these equations to Mathematica and solve for x1 and y1:
>
> Which format is the best for importing?
>
> Thanks
>
> Tugrul
>
>
>
>
>
> 



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