Using trapz function to provide answers using loop
显示 更早的评论
Hey,
I am trying to use the trapz function in a loop:
y_approx = zeros ([21 1]);
for i = 1:length(x)
y_approx = trapz(x(i),y)
end
It is providing me the 21 answers but they are incorrect. I think it is using the 21 y for each iteration of x. 21 y values for 1 x value, 21 y values for 2 x values etc. How do I alter the code to make it use the same number of y values as x values?
采纳的回答
% The way to use trapz
x= 1:20; % x
y = randn(20, 1); % y
ytrapz = trapz(x, y) % integral y dx
4 个评论
Dyl
2022-9-28
So this is what you want? You don't need trapz function
x= 1:20; % x
y = randn(20, 1); % y
ytrapz = trapz(x, y) % integral y dx
yloop = zeros(size(x));
for i=2:length(x)
yloop(i) = yloop(i-1) + (y(i) + y(i-1))/2*(x(i)-x(i-1));
end
yloop([1:3 end-3:end])
Dyl
2022-9-28
That is not really necessary since the looping code above is doing the trapz job in a more efficient way when you want the intermidiate results.
However, if you insisit, you can do the following (definitely not recommended):
x= 1:20; % x
y = randn(20, 1); % y
ytrapz = trapz(x, y) % integral y dx
yloop = zeros(size(x));
for i=2:length(x)
yloop(i) = yloop(i-1) + (y(i) + y(i-1))/2*(x(i)-x(i-1));
end
yloop([1:3 end-3:end])
% Not recommended:
yloop1 = zeros(size(x));
for i=2:length(x)
yloop1(i) = trapz(x(1:i), y(1:i));
end
yloop1([1:3 end-3:end])
更多回答（0 个）
类别
在 帮助中心 和 File Exchange 中查找有关 Numerical Integration and Differentiation 的更多信息
Translated by 
