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function c = relation( n ) if n==0 c = 1; elseif n==1 syms x c = [x 0]; else syms x c = ((2*n-1)*x*[relation(n-1),0] - (n-1)*[0,0,relation(n-2)])/n; sum(c) end n=8 m=n+1; xval=linspace(-1,1,5000) I=trapsum(polyval(relation(n),xval).*polyval(relation(m),xval),-1,1);
Gives the following output:
??? Error using ==> polyval Inputs to polyval must be floats, namely single or double.
Error in ==> polyval at 63 y = zeros(siz_x, superiorfloat(x,p));
What needs to be done to ensure that the output for the recurrence relation is a double?
I mean, in the function, we have syms x but this is to acquire the polynomial in analytic form. It's not necessary in this case but I need to plot it later on. The main issue I have is evaluating the integral using trapsum but I would need to do both; plot for various n, evaluate the integral.
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In your code for relation(), why do you have
which is just displaying the sum rather than returning the sum ?
After you build the relation symbolically, use
RelationM = relation(m); RelationN = relation(n); funM = matlabFunction(RelationM); funN = matlabFunction(RelationN); Y = funM(xval) .* funN(xval);
trapsum(Y, -1, 1)
However, I do not know what your trapsum routine does: it is not a routine in any Mathworks toolbox, and the obvious trapsum in the File Exchange uses a different calling sequence.
Get rid of the "syms x". You are doing only numerical manipulations with the polynomial so there is no apparent need to have it in symbolic form, and that includes for plotting. Example
t=linspace(-1,1,1000); p=[1 2 1]; %polynomial coefficients plot(t,polyval(p,t))
Also, why use trapsum instead of the builtin trapz?