Trapz gives "Second and third argument must either be variables or a variable and a nonnegative integer specifying the number of differentiations."

Question

Amrit Lohia 2019-12-3

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/494509-trapz-gives-second-and-third-argument-must-either-be-variables-or-a-variable-and-a-nonnegative-inte

回答： Stephan 2019-12-3

Why does the following not work:

f_scalar = @(x) 5*x^2+3*x-4; g_scalar = @(x) -4*x^2+6*x+5;
f = @(vec) arrayfun(f_scalar,vec); g = @(vec) arrayfun(g_scalar, vec); 
points = solve(f(x) == g(x), x);
h = @(x) g(x) - f(x);
vals = linspace(points(1),points(2),100);
disp(trapz(vals,h(vals)));

It gives "Error using sym/diff (line 36)

Second and third argument must either be variables or a variable and a nonnegative integer specifying the

number of differentiations."

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephan 2019-12-3

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/494509-trapz-gives-second-and-third-argument-must-either-be-variables-or-a-variable-and-a-nonnegative-inte#answer_404431

在 MATLAB Online 中打开

syms x
f_scalar = @(x) 5*x^2+3*x-4; g_scalar = @(x) -4*x^2+6*x+5;
f = @(vec) arrayfun(f_scalar,vec); g = @(vec) arrayfun(g_scalar, vec); 
points = solve(f(x) == g(x), x);
points = double(points);
h = @(x) g(x) - f(x);
vals = linspace(points(1),points(2),100);
disp(trapz(vals,h(vals)));