The Math Forum

Search All of the Math Forum:

Views expressed in these public forums are not endorsed by NCTM or The Math Forum.

Math Forum » Discussions » Software » comp.soft-sys.matlab

Notice: We are no longer accepting new posts, but the forums will continue to be readable.

Topic: how to convert a symbolic system into its matrix form
Replies: 2   Last Post: Apr 6, 2013 3:25 PM

Advanced Search

Back to Topic List Back to Topic List Jump to Tree View Jump to Tree View   Messages: [ Previous | Next ]
Christopher Creutzig

Posts: 323
Registered: 2/24/09
Re: how to convert a symbolic system into its matrix form
Posted: Apr 4, 2013 5:10 AM
  Click to see the message monospaced in plain text Plain Text   Click to reply to this topic Reply

On 14.03.13 18:18, pietro wrote:
> Hi all,
> I have a symbolic system and I have to convert it in its matrix form. As example:
> a*x+b*y=2;
> c*x+d*y=5;
> in
> [a,b;c,d]*[x;y]=[2;5];
> Is there anyway to perform that with matlab2012a? I know there is the function equationsToMatrix for the 2013a version, but unfortunately I don't have it. :(

You could try to make polynomial expressions from the equations with the
?children? function and then use ?quorem(lhs, x, x)? and ?quorem(lhs, y,
y)? to get the vectors to combine into the matrix. Not really pretty, I

>> eqs = [a*x+b*y==2; c*x+d*y==5];
>> lhsrhs = children(eqs);
>> lhsrhs = cellfun(@(x) x(1)-x(2), lhsrhs, 'UniformOutput', false);
>> lhsrhs = [lhsrhs{:}].'

lhsrhs =

a*x + b*y - 2
c*x + d*y - 5

>> [quorem(lhsrhs, x, x), quorem(lhsrhs, y, y)]

ans =

[ a, b]
[ c, d]


Point your RSS reader here for a feed of the latest messages in this topic.

[Privacy Policy] [Terms of Use]

© The Math Forum at NCTM 1994-2018. All Rights Reserved.