Symbols vs Floating points

2012 3 28
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This question has to do with the question in this link which Jan has kindly shed some light on.
http://www.mathworks.co.uk/matlabcentral/answers/33744-error-using-odearguments
As mentioned in my comment, I am wondering why my x0 is of class 'sym'. I tried playing around with it and discovered that the problem lies with c0=f(a0,b0).
But I don't know what I can do with it to make it a 'double'. The thing is c0 is a number, no?

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Richard
Richard 2012-3-28
When I run the code without c0, I get, for example
{x0 =
10 10}
class(x0)=double
whereas with c0, I get
{x0=
[10, 10, 20]}
,say, and
class(x0)=sym
So Matlab does get numbers, I don't know why the square brackets though and why the class.
Jan
Jan 2012-3-28
Please post the definition of "f", "a0" and "bo". Otherwise we cannot guess what's going on.
Jan
Jan 2012-3-28
The square brackets mean, that the value is a vector. I'm not sure, why the curly braces appear.
Richard
Richard 2012-3-28
Thanks, Jan.
f = @(a,b) diff(100*a^5+b, sym('a'));
a0=10;
b0=10;
c0=f(a0,b0);
x0 = [a0,b0,c0];
The curly brackets aren't actually there (though the square ones are) -- I thought that using the curly ones in this forum gives the code font -- sorry it is really me being stupid!
Jan
Jan 2012-3-28
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Jan
Jan 2012-3-28

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Your f contains the term "sym('a')". Therefore the results get the type sym also. Perhaps you want to use the command double to make the symbolic expression numerically.

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