问题描述
对于x = 0到pi / 2和y = 0到pi / 2,我无法集成heaviside(y-f)(仅对syms集成“ int”)。运行代码后,输出如下所示,但我无法获得数字答案。您可以提出一些有关如何进行的想法吗?
代码:
syms x y
f = sin(x);
integ = int( int(heaviside(y-f),x,pi/2),y,pi/2)
结果:
integ =
int(int(heaviside(y - sin(x)),pi/2)
解决方法
尽可能避免进行符号计算。
注意,heaviside函数可以定义为:
hvsd = @(x) (x > 0) + 0.5*(x == 0); % another name to do not overshadow heaviside
heaviside = @(x) (x > 0) + 0.5*(x == 0);
fun = @(x,y) heaviside(y-sin(x));
% using integral2
I1 = integral2(fun,pi/2,pi/2)
nx = 100; ny = 100;
x = linspace(0,nx);
y = linspace(0,ny);
[X,Y] = meshgrid(x,y);
Z = fun(X,Y);
% using trapz
I2 = trapz(y,trapz(x,Z.*(Z>0),2))
I1 = 1.4674 I2 = 1.4695