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

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!

Answer 1

[Cris LaPierre]

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.

[Roxanne Esguerra]

Thanks! I put

axis equal

in each subplot.

I also put the 0.5 increment to the t-values.

This is the result I got (the axes are the same with the previous one and I still didn't get a circle for the last plot...) Do you have any other suggestions?

[Roxanne Esguerra]

I tried using

axis vis3d

and it somehow worked :)

[Roxanne Esguerra]

Thanks for the help :)

[Cris LaPierre]

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.

[Cris LaPierre]

Oh, great! Glad it worked.

Answer 2

[Arthur Roué]

A call to

axis equal

After creating your plot will set the same length for the data units along each axis.

[Roxanne Esguerra]

I tried adding that to each subplot and it still didn't result to the required scaling of the axes.

Is it possible to have increments in the axis limits?

[Roxanne Esguerra]

Thanks for the help :)