How to change the scale of plot axes? How to plot circle using separate x and y equations?

Question

Roxanne Esguerra 2020-7-23

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/569529-how-to-change-the-scale-of-plot-axes-how-to-plot-circle-using-separate-x-and-y-equations

评论： Cris LaPierre 2020-7-24

采纳的回答： Cris LaPierre

在 MATLAB Online 中打开

Hi, I need to have this kind of result: (the scaling of the axes, and the graph of the 3rd and 6th subplots)

Here is my code:

for k = 1:6
    ax(k) = subplot(3,3,k);
end
subplot(ax(1))
fplot(@(x) cos(x))
xlabel('x')
ylabel('y')
title('cos(x)')
axis([-5 5 -1 1])
subplot(ax(2))
fplot(@(x) cos(x))
xlabel('x')
ylabel('y')
title('cos(x)')
axis([0 2 -1 1])
subplot(ax(3))
fimplicit(@(x,y) (1/y)-(log(y))+(log(-1+y))+x-1)
xlabel('x')
ylabel('y')
title('1/y-log(y)+log(-1+y)+x-1=0')
axis([-5 5 -5 5])
subplot(ax(4))
fimplicit(@(x,y) x^2+y^2-4)
xlabel('x')
ylabel('y')
title('x^2+y^2-4=0')
axis([-5 5 -5 5])
%Plot for x^3+y^3-5xy+1/5=0
subplot(ax(5))
fimplicit(@(x,y) x^3+y^3-(5*x*y)+(1/5))
xlabel('x')
ylabel('y')
title('x^3+y^3-5xy+1/5=0')
axis([-2 2 -3 3])
t = -5:5;
x = sin(t);
y = cos(t);
subplot(ax(6))
plot(x,y)
xlabel('x')
ylabel('y')
title('x = sin(t),y = cos(t)')
axis([-0.5 0.5 -1 1])

This is the result I get using my code:

Thank you in advance!

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

Cris LaPierre 2020-7-23

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/569529-how-to-change-the-scale-of-plot-axes-how-to-plot-circle-using-separate-x-and-y-equations#answer_469863

在 MATLAB Online 中打开

Try adding 'axis equal'. You can see additional options here.

You already have the equations for getting X and Y of a circle. The problem is your resolution. Too few points, and your circle might look like an octogon, or a square. The circle will look smoother the smaller the step between each point is. Adjust this by modifying t. For example

t = -5:0.5:5

See here for more. Change the value in the middle until you get the output you like.

5 个评论
显示 3更早的评论隐藏 3更早的评论

Cris LaPierre 2020-7-24

Axis equal makes the scale the same in x and y. This is not applicable for every single subplot. For example, the top left has a range in Y of 2, but a range of 10 in X.

Also note that this is a 2x3 suplot grid, not 3x3.

Fix the warnings you get in the code by using elementwise operators in your equations.

Note that, at least for the trig functions, it's most likely the limits are some multiple of pi.

This is clearly an exercise to get you to explore various axis properties - limits, modes, etc. You do not do the same thing in every plot.