How do I numerically integrate a multivariable function wrt only one variable?

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Martijn Mouw
Martijn Mouw 2018-7-9
编辑： Matt J 2018-7-9
Hi guys,
I have a problem, since I want to numerically intergrate a multivariable function wrt only one variable. However, I only succeed by doing this with the following commands:
if true
clear
syms r s t
p0 = .75;
p1 = 3;
y0 = 720;
b = [5 -14 0.08];
end
if true
function demand = qn(x,b)
z1=b(1)+b(2)*x(1)+b(3)*x(2);
demand = z1;
end
if true
w(r,s) = int(qn([t, y0],b),t,r,s);
cs = w(p0,p1);
end
I know this is not a numerical integration. This returns me a symbolic variable (which I do not want), but this was the only way that I was able to retrieve some value. To clarify, I want to numerically integrate the function qn with respect to x(1) from p0 to p1. Could somebody help me with this please? Many thanks in advance! Cheers!

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Matt J
Matt J 2018-7-9
编辑：Matt J 2018-7-9
p0 = .75;
p1 = 3;
b = [5 -14 0.08];
x2=...
result = integral( @(x1) qn([x1,x2],b) , p0, p1)
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Matt J
Matt J 2018-7-9
In this case, it would be much easier if you wrote qn() with scalar arguments,
function demand = qn(t,y,b)
z1=b(1)+b(2)*t+b(3)*y;
demand = z1;
end
then this would work
result = integral( @(t) qn(t,y0,b) , p0, p1)
Martijn Mouw
Martijn Mouw 2018-7-9
Thanks this works! I know that indeed with scalar arguments it would be easier, but it has to stay the way it is for other commands work (I did not include them in the post)

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