How to identify points on a graph of multiple functions

Question

Samuel Eronmwon 2023-2-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1907015-how-to-identify-points-on-a-graph-of-multiple-functions

评论： Samuel Eronmwon 2023-2-9

I wish to identify the point where y=0 for four functions on the same figure with a dot. I understand that interp1 can be used do this but I plotted my functions using "fplot" and it seems that Interp1 doesn't work with fplot. So how do I do this?

Here is my code;

n1= exp(1);

n2= 2.95;

n3= 3.05;

n4= pi;

figure;

f1 = @(x) n1-tan((x-(pi/4))/5);

fplot(f1,[0,8])

hold on

f2 = @(x) n2-tan((x-(pi/4))/5);

fplot(f2,[0,8])

hold on

f3 = @(x) n3-tan((x-(pi/4))/5);

fplot(f3,[0,8])

hold on

f4 = @(x) n4-tan((x-(pi/4))/5);

fplot(f4,[0,8])

grid on

title('Plot of Functions')

xlabel('Y values')

ylabel('X values')

legend('n=e','n=2.95','n=3.05','n=pi')

Using Snipping tool, this is what I want to produce

Those coloured dots such that when hovered over it displays the values.

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Answer 1

Tushar Behera 2023-2-6

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https://ww2.mathworks.cn/matlabcentral/answers/1907015-how-to-identify-points-on-a-graph-of-multiple-functions#answer_1164400

编辑：Tushar Behera 2023-2-6

在 MATLAB Online 中打开

Hi Samuel,

I believe you want to identify spots where y=0 on your plot.

To find the x values where y=0 for each function, you can use the fsolve function. fsolve finds the roots of a function, so you can use it to find the x values where each function crosses the y=0 line. Here's an example of how you can find the roots and plot them on the same figure:

n1= exp(1);
n2= 2.95;
n3= 3.05;
n4= pi;
figure;
f1 = @(x) n1-tan((x-(pi/4))/5);
fplot(f1,[0,8])
hold on
f2 = @(x) n2-tan((x-(pi/4))/5);
fplot(f2,[0,8])
hold on
f3 = @(x) n3-tan((x-(pi/4))/5);
fplot(f3,[0,8])
hold on
f4 = @(x) n4-tan((x-(pi/4))/5);
fplot(f4,[0,8])
grid on
% Find the roots using fsolve
x1 = fsolve(f1,pi/4);
x2 = fsolve(f2,pi/4);
x3 = fsolve(f3,pi/4);
x4 = fsolve(f4,pi/4);
% Plot the roots on the same figure
scatter(x1, 0, 'ro');
scatter(x2, 0, 'ro');
scatter(x3, 0, 'ro');
scatter(x4, 0, 'ro');
title('Plot of Functions with Roots')
xlabel('Y values')
ylabel('X values')
legend('n=e','n=2.95','n=3.05','n=pi')