Display maximal value in a range?

Question

Desiree 2019-8-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475659-display-maximal-value-in-a-range

评论： Star Strider 2019-8-10

Hello. I would like to display the max(abs(sigma)) from around t=7 to t=10 from this code. The plot is from 0 to 10 and I tried to display that max value but it shows me the maximum value from the whole range (from 0 to 10) instead from 7 to 10. How can I do it? Here’s my code:

clear all
t=0;% initial time
x=[1,1,1];% initial condition for t=0
alpha=30;
tau=0.0001;
k=1; % counter
while t<=10
    f=-sin(t+5)-0.5*cos(t)-x(2);
    v=x(1);
    vc=sin(t+1)-cos(0.5*t-2);
    vcc=cos(t+1)+0.5*sin(0.5*t-2);
    sigma=v-vc;
    sigmadot=f-vcc;
    u=alpha*((abs(sigmadot)).^2*sign(sigmadot)+sigma)/((sigmadot).^2+abs(sigma));
    dx=[f,cos(1+x(1)+x(3))+(2-cos(x(1)+x(3)+1))*u,cos(x(1)+0.5*x(3)-t)-x(3)+u];
    x=x+dx*tau;
    t=t+tau;
    sigmav(k)=sigma;
    sigmadotv(k)=sigmadot;
    tv(k)=t;
    k=k+1;
end
figure
plot(tv,sigmav,'b',tv,sigmadotv,'r')

Help is appreciated!

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Answer 1

Star Strider 2019-8-10

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475659-display-maximal-value-in-a-range#answer_387064

编辑：Star Strider 2019-8-10

在 MATLAB Online 中打开

I do not see any max function calls, so I am not certain what result you want.

Displying only the values for ‘tv’ between 7 and 10 is straightforward:

Lidx = (tv>=7) & (tv<=10);
figure
plot(tv(Lidx),sigmav(Lidx),'b',tv(Lidx),sigmadotv(Lidx),'r')

with ‘Lidx’ being the logical index vector. This will select the values of the vectors you want.

To display ‘max(abs(sigma))’, assuming you intend ‘sigmav’:

maxSigma = max(abs(sigmav(Lidx)))
maxSigma =
     4.451070235722554e-07

If you simply want to restrict the plot, you can also do that with the xlim function.

If you want to display it on the plot, use the text function.

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Desiree 2019-8-10

Once again thanks a lot for the help!

Star Strider 2019-8-10

As always, my pleasure!

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Answer 2

KALYAN ACHARJYA 2019-8-10

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/475659-display-maximal-value-in-a-range#answer_387065

编辑：KALYAN ACHARJYA 2019-8-10

在 MATLAB Online 中打开

"I would like to display the max(abs(sigma)) from around t=7 to t=10 from this code"

Is this one:

t=0;% initial time
x=[1,1,1];% initial condition for t=0
alpha=30;
tau=0.0001;
k=1; % counter
l=1;
while t<=10
    f=-sin(t+5)-0.5*cos(t)-x(2);
    v=x(1);
    vc=sin(t+1)-cos(0.5*t-2);
    vcc=cos(t+1)+0.5*sin(0.5*t-2);
    sigma=v-vc;
    %% I haved changed Here
    if t>=7 & t<=10
        sigma_update(l)=sigma;
        l=l+1;
    end
    %%
    sigmadot=f-vcc;
    u=alpha*((abs(sigmadot)).^2*sign(sigmadot)+sigma)/((sigmadot).^2+abs(sigma));
    dx=[f,cos(1+x(1)+x(3))+(2-cos(x(1)+x(3)+1))*u,cos(x(1)+0.5*x(3)-t)-x(3)+u];
    x=x+dx*tau;
    t=t+tau;
    sigmav(k)=sigma;
    sigmadotv(k)=sigmadot;
    tv(k)=t;
    k=k+1;
end
figure
plot(tv,sigmav,'b',tv,sigmadotv,'r');
disp(max(abs(sigma_update)));