MATLAB: Graphing and converting sym p to long (or double) p.

symSymbolic Math Toolbox

>>x=linspace(-1,1,100) >>p = 1/26 + 25/26*x- (25/26*x-25/26)*x + ((625/1313*x-1250/1313)*x-625/1313)*x >> plot(x,double(p))

??? Error using ==> eval Undefined function or variable 'x'. Error in ==> sym.double at 45 D = reshape(eval(X),siz);

Questions: (1) How do I convert sym x (lower case variable x) to long (because I wanted it to be to the 16th decimal places)? (2) How do I get this Polynomial expression called 'p' to graph along a linspace between -1 and 1 of 100 intervals between them?

Best Answer

Thank you so much. You answered 2 questions in 1 command. You R-O-C-K!!!

Related Solutions

MATLAB: Integrating from polyint(p)

Sorry, but polyint cannot integrate a rational polynomial, and certainly not over an infinite region. Depending on the roots of the polynomial, it may or may not have an integral.

The simplest way to do your integration is to use the symbolic toolbox.

syms x
P = x^4 + 8*x^3 + 23*x^2 + 28*x + 12;
int(x/P,x,[1,inf])
ans =
log((3*2^(1/2))/8) + 2/3

If you have only the coefficients of the polynomial, you can still do it.

pcoeff = [1 8 23 28 12];
roots(pcoeff)
ans =
           -3
           -2
           -2
           -1

So a happy list of roots.

int(x/poly2sym(pcoeff,x),[1,inf])
ans =
log((3*2^(1/2))/8) + 2/3

MATLAB: I have problem in uses of inline or syms ordes

syms x
f = x^2+x+1;
subs(f^2,x,1)

Best Answer

Related Solutions

MATLAB: Integrating from polyint(p)

MATLAB: I have problem in uses of inline or syms ordes

Related Question