How to plot a smooth graph?

Question

donghun lee 2020-4-2

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514796-how-to-plot-a-smooth-graph

评论： donghun lee 2020-4-2

clc,clear all

b0 = 0.015;
b1 = 0.015;
b2 = 0.035;
b3 = 0.050;
v = 40; %velocity
L = 2;
w = (2*pi*v)/L; %angular frequency
F = w*(1/(2*pi)); %in Hz
t = linspace(0,10,18);
b = b0 + b1*sin(w*t) + b2*sin(2*w*t) 
+b3*sin(3*w*t);
plot(t,b)

Hi, I want to make this graph as being a smooth graph.

Thank you for your time.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Rik 2020-4-2

Although you could resample your function to draw a smooth curve through your data points, that would not accurately describe your function. You can greatly increase the number of points in your t vector to see that you have an enormous amount of aliasing going on here. See this Wikipedia page for more information.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Birdman 2020-4-2

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/514796-how-to-plot-a-smooth-graph#answer_423514

编辑：Birdman 2020-4-2

在 MATLAB Online 中打开

You need to increase the step size of your t vector:

t = linspace(0,10,100);

Code:

b0 = 0.015;
b1 = 0.015;
b2 = 0.035;
b3 = 0.050;
v = 40; %velocity
L = 2;
w = (2*pi*v)/L; %angular frequency
F = w*(1/(2*pi)); %in Hz
t = linspace(0,10,100);
b = b0 + b1*sin(w*t)+b2*sin(2*w*t)+b3*sin(3*w*t);
plot(t,b)

5 个评论
显示 3更早的评论隐藏 3更早的评论

Rik 2020-4-2

在 MATLAB Online 中打开

That is why I suggested to zoom in. The weirdness is not from me, but actually from your function. If you want a true plot of your function you should increase the number of samples until further increasing it no longer changes your graph. For this function that starts at about 2500 samples. With about 10000 samples I no longer notice an improvement in smoothness.

You could avoid having to do this yourself by using fplot:

b0 = 0.015;
b1 = 0.015;
b2 = 0.035;
b3 = 0.050;
v = 40; %velocity
L = 2;
w = (2*pi*v)/L; %angular frequency
F = w*(1/(2*pi)); %in Hz
t_max=10;
b_fun =@(t) b0 + b1*sin(w*t)+b2*sin(2*w*t)+b3*sin(3*w*t);
fplot(b_fun,[0 t_max])
axis([0 1 -0.125 0.125])%zoom in to see detail