Make Function Equal Zero After Certain Time

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s.v. 2018-4-4

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/392711-make-function-equal-zero-after-certain-time

评论： Star Strider 2018-4-4

Hi all, I am in need of some help. I am trying to use if and else statements to plot the following function. Here is my current code:

HP = 60/72;
Tas = 0.105;
Elamin = 0.12;
Elamax = 0.28;
Eramin = 0.05;
Eramax = 0.15;
t = [0:0.001:HP]; 
     if t > Tas
          aa = 0;
      else
          aa = sin((pi*t)/Tas);
      end
ela = Elamin + (Elamax - Elamin)*aa;
era = Eramin + (Eramax - Eramin)*aa;
plot(t,ela, t,era, t,aa);

Basically, I am trying to say that for 0<t<Tas, the function aa is calculated. Otherwise, the function aa = 0. Attached is the current plot I am getting if I do not include the if/else statements. Its kind of what I want, except the graph must level to around y = 0 after x = Tas (about 0.105s).

Any help is appreciated!

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Answer 1

Star Strider 2018-4-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/392711-make-function-equal-zero-after-certain-time#answer_313533

在 MATLAB Online 中打开

Try this:

aa = @(t, Tas) sin((pi*t)/Tas) .* ((0 <= t) & (t <= Tas));      % Function, With Conditions As A Logcal Index Vector
t = linspace(-1, 1, 150);                                       % Time Vector
Tas = 0.105;
figure
plot(t, aa(t, Tas))
grid

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Star Strider 2018-4-4

在 MATLAB Online 中打开

An image would be easier to work with than a .fig file that requires us to download it and then view it before again deleting the file. It’s been a long day and I choose not to do that.

Try this:

aa_fcn = @(t, Tas) sin((pi*t)/Tas) .* ((0 <= t) & (t <= Tas));      % Function, With Conditions As A Logcal Index Vector
HP = 60/72;
t = linspace(-1, HP, 150);                                          % Time Vector
Tas = 0.105;
aa = aa_fcn(t, Tas);
Elamin = 0.12;
Elamax = 0.28;
Eramin = 0.05;
Eramax = 0.15;
ela = Elamin + (Elamax - Elamin)*aa;
era = Eramin + (Eramax - Eramin)*aa;
figure
plot(t,ela, t,era, t,aa);
grid
legend('ela', 'era', 'aa')
N = 7;                                                              % Number Of Repititions
t_ext = linspace(0, HP*N, numel(t)*N);                              % Extend ‘t’ For ‘N’ Repititions
ela_ext = repmat(ela, 1, N);                                        % Extend ‘ela’ For ‘N’ Repititions
era_ext = repmat(era, 1, N);                                        % Extend ‘era’ For ‘N’ Repititions
aa_ext  = repmat(aa, 1, N);                                         % Extend ‘aa’ For ‘N’ Repititions
figure
plot(t_ext,ela_ext, t_ext,era_ext, t_ext,aa_ext);
grid
legend('ela', 'era', 'aa')

The ‘N’ variable will scale the previously-defined vectors to produce the desired number of repetitions.

Experiment to get the result you want.

s.v. 2018-4-4

Thank you.

Star Strider 2018-4-4

As always, my pleasure.

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Make Function Equal Zero After Certain Time

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Make Function Equal Zero After Certain Time

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