Make Function Equal Zero After Certain Time

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!

Answer 1

[Star Strider]

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

[s.v.]

That is more of what I am looking for, but writing aa in that form doesn't allow me to plot ela or era anymore. I get the error:

"Undefined operator '*' for input arguments of type 'function_handle'."

What else must I change?

Thanks!

[Star Strider]

I forgot to include ‘ela’ and ‘era’.

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')

[s.v.]

That worked. If you'd like to help further -- I'd like to have the same waveform shown in the attached figure happen over 6 seconds. So basically, the attached figure multiple times on 1 graph (graph starts every 0.8 sec).

[Star Strider]

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.]

Thank you.

[Star Strider]

As always, my pleasure.