Connecting dots in a plot

Question

Anton Dor 2020-5-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526339-connecting-dots-in-a-plot

评论： Star Strider 2020-5-18

Hi, I need to connect the dots of the plot I'm getting. But when I try to replace the 'x' with '-' I don't see the line in the plot. I tried also to have the line in various colors but but with not luck so far.

Any help is appreciated, see code below:

Thanks.

function [] = HW3_Main_Code()
clc;
clear all;
gama=2.8;
Hmo=2;
% Constants definitions:
time=20; % Measurement time
f1=0.02;
f=f1:f1:time;
eta=1:f1:time;
Tp=5.45*sqrt(Hmo); % By correlation of wave measurements around Israel
alpha=0.064/(0.23+0.0336*gama-0.185/(1.9+gama)); % Normalization factor which is calculated to satisfy the relation Hmo=4*sqrt(mo)
for t=1:time
    if f(t)<(1/Tp) sigma=0.07;
        else sigma=0.09;
    end
    S=alpha*((Hmo^2)/(Tp^4))*((f(t))^(-5))*exp(-(5/4)*((Tp*(f(t)))^(-4)))*gama^(exp(-(1/2*sigma^2)*((Tp*(f(t))-1)^2)));
    a=sqrt(2*S*f1);
    phi=2*pi*rand(1,1); % random phase between 0 and 2*pi
    omega=2*pi*f(t);
    eta(t)=a*cos(omega*t+phi);
    plot(t,eta(t),'x');
    title('\eta - Real Sea Water Surface','Fontsize',8); ylabel('\eta [m]','Fontsize',8); xlabel('t [sec]','Fontsize',8);
    hold on
end

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Answer 1

Star Strider 2020-5-18

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/526339-connecting-dots-in-a-plot#answer_433135

在 MATLAB Online 中打开

Try this:

gama=2.8;
Hmo=2;
% Constants definitions:
time=20; % Measurement time
f1=0.02;
f=f1:f1:time;
% eta=1:f1:time;
Tp=5.45*sqrt(Hmo); % By correlation of wave measurements around Israel
alpha=0.064/(0.23+0.0336*gama-0.185/(1.9+gama)); % Normalization factor which is calculated to satisfy the relation Hmo=4*sqrt(mo)
tv=1:time;
for k = 1:numel(tv)
    t = tv(k);
    if f(t)<(1/Tp) sigma=0.07;
        else sigma=0.09;
    end
    S=alpha*((Hmo^2)/(Tp^4))*((f(t))^(-5))*exp(-(5/4)*((Tp*(f(t)))^(-4)))*gama^(exp(-(1/2*sigma^2)*((Tp*(f(t))-1)^2)));
    a=sqrt(2*S*f1);
    phi=2*pi*rand(1,1); % random phase between 0 and 2*pi
    omega=2*pi*f(t);
    eta(k)=a*cos(omega*t+phi);
%     plot(t,eta(t),'x');
%     title('\eta - Real Sea Water Surface','Fontsize',8); ylabel('\eta [m]','Fontsize',8); xlabel('t [sec]','Fontsize',8);
%     hold on
end
figure
plot(tv,eta,'-x');
title('\eta - Real Sea Water Surface','Fontsize',8); ylabel('\eta [m]','Fontsize',8); xlabel('t [sec]','Fontsize',8);

I created the ‘tv’ vector from ‘t’ and eliminated the first definition of ‘eta’ defining it only in the loop, and moved the plot call outside (after) the loop .

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Anton Dor 2020-5-18

Thank you, it works, can you please explain further what you did?

What is numel?

Star Strider 2020-5-18

My pleasure!

I essentially explained everything already, in the sentence after the code I posted.

Providing more detail, I eliminated the original definition of ‘eta’ (that was causing problems), then created ‘tv’ from the original ‘t’ vector and then created inidividual instances of ‘t’ from it in each iteration of the loop, using each of those to calculate an element of ‘eta’. The code then plotted both vectors (‘tv’ and ‘eta’) after the loop completed.

Plotting vectors rather than individual values allows connecting lines, because the plot function connects pairs of points with lines (if that is desired), the reason that plotting individual points within the loop failed to connect them with lines. Plotting individual points in each iteration provides no point-pairs to connect, so no lines appear between them.

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