How can I make double integration

syms x;
syms r;
for n=1:10
    for i=2:t
        f1(i,n) = h * (Sast(i-1,n) + r* Y(i,n) - x) * 1 / (v(i,n)^(1/2) * sig(n) * (2 * pi)^(1/2)) * exp((-(x-m(i,n))^2) / (2 * v(i,n) * sig(n)^2)) * unifpdf(r,A(fv),B(fv));
        f2(i,n) = -p * (Sast(i-1,n) + r * Y(i,n) - x) * 1 / (v(i,n)^(1/2) * sig(n) * (2 * pi)^(1/2)) * exp((-(x-m(i,n))^2) / (2 * v(i,n) * sig(n)^2)) * unifpdf(r,A(fv),B(fv));
        z(i,n)=f1(i,n)+f2(i,n)
        C2_1(i,n)=dblquad(z(i,n),inf,Sast(i-1,n),-inf,Sast(i-1,n))
        %C2_1(i,n) = int(int(f1(i,n), x, inf, Sast(i-1,n) + r(i,n,fv)*Y(i,n)), y, inf, Sast(i-1,n) + r(i,n,fv)*Y(i,n)) + int(int(f2(i,n), x, Sast(i-1,n) + r(i,n,fv)*Y(i,n), -inf), y, inf, -inf);
        %C2_1(i,n) = dblquad(f1(i,n), inf, Sast(i-1,n) + r(i,n,fv)*Y(i,n), inf, Sast(i-1,n) + r(i,n,fv)*Y(i,n)) + dblquad(f2(i,n), Sast(i-1,n) + r(i,n,fv)*Y(i,n), -inf, Sast(i-1,n) + r(i,n,fv)*Y(i,n), -inf);
    end
end

I made lots of code..but can't sure why it's not work

[José-Luis]

And what does the debugger say? What does "does not work" mean?

[Sunghye]

Error using fcnchk (line 103) If FUN is a MATLAB object, it must have an feval method.

Error in dblquad (line 54) intfcn = fcnchk(intfcn);

Error in work03 (line 159) C2_1(i,n)=dblquad(z(i,n),inf,Sast(i-1,n),-inf,Sast(i-1,n))

[Walter Roberson]

Yes, because sym objects do not have an feval() method.

Answer 1

[Walter Roberson]

You are creating f1 and f2 as symbolic expressions, but you are attempting ot use dblquad() to do the integration. dblquad() takes a function handle, not a symbolic expression. Try

C2_1(i,n)=dblquad(matlabFunction(z(i,n)),inf,Sast(i-1,n),-inf,Sast(i-1,n))

Are you sure you want to go from +infinity downward to Sast(i-1,n) for the first variable? You go from -infinity upward to Sast(i-1,n) for the second variable.

[Sunghye]

Thank you, Walter It works!!! However, the answer is NaN(maybe not a NUMBER) What's the NaN mean?

error message is following

Warning: Infinite or Not-a-Number function value encountered. > In quad at 105 In dblquad>innerintegral at 82 In quad at 72 In dblquad at 58 In work03 at 159