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using for loop plotting problem help me

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ataberk kaplica
ataberk kaplica on 12 Jan 2021
Commented: Rik on 12 Jan 2021
function homework
f= @(x) 3*x^5+7*sind(x)^2;
fd= @(x) 15*x^4+7*sind(2*x)^2+3*x^5+7*sind(x)^2;
a=-1;
b=3;
n=5;
e=1.1*10^3;
s=(fd(a)+fd(b));
for i=1:1:n-1
h=(b-a)/i;
s=s+2*fd(i);
I=(h/2).*s
error=I-e
end
end
the problem is ı have values but try everything for plotting but see nothing even there is no line or spline .

  3 Comments

Cris LaPierre
Cris LaPierre on 12 Jan 2021
Why do you expect to see a plot? You haven't included any plotting commands. See Ch 9 of MATLAB Onramp for help with plotting.
ataberk kaplica
ataberk kaplica on 12 Jan 2021
i did all plot type , but get nothing
Rik
Rik on 12 Jan 2021
This time I edited your question for you (also removing most blank lines). Next time, please use the tools explained on this page to make your question more readable.
I don't understand your comment. Your function does not contain any plotting functions, and at the end of a function all variables that aren't output variables will be wiped.
Also, you overwrite the contents of you variables every iteration of your loop. You may also want to look at the Onramp part concerning loops and indexing.

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Accepted Answer

Mathieu NOE
Mathieu NOE on 12 Jan 2021
hello
I assumed that you wanted to plot I and error , but you forgot to index thos variables
see below :
f= @(x) 3*x^5+7*sind(x)^2;
fd= @(x) 15*x^4+7*sind(2*x)^2+3*x^5+7*sind(x)^2;
a=-1;
b=3;
n=5;
e=1.1*10^3;
s=(fd(a)+fd(b));
for i=1:1:n-1
h=(b-a)/i;
s=s+2*fd(i);
I(i)=(h/2).*s;
error(i)=I(i)-e;
end
figure(1),plot(1:n-1,I,'b')
figure(2),plot(1:n-1,error,'r')

  6 Comments

Show 3 older comments
Rik
Rik on 12 Jan 2021
Just a note: you should avoid using function names as variable names. It is very common to want to use the error function, so shadowing it is a bad habit (similar to max, mean, and sum).

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More Answers (1)

David Hill
David Hill on 12 Jan 2021
What are you trying to plot?
f= @(x) 3*x.^5+7*sin(x).^2;%I doubt you want sind
fd= @(x) 15*x.^4+7*sin(2*x).^2+3*x.^5+7*sin(x).^2;
x=-1:.01:3;
plot(x,f(x),x,fd(x));

  1 Comment

ataberk kaplica
ataberk kaplica on 12 Jan 2021
I am trying to error vs h graph for n 1-10 range

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