using for loop plotting problem help me

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 .

[Cris LaPierre]

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]

i did all plot type , but get nothing

[Rik]

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.

Answer 1

[Mathieu NOE]

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')

[ataberk kaplica]

yes thank you but more like ı want to error vs h graph how can ı do that

[ataberk kaplica]

for 1:n-1 range

[Mathieu NOE]

ok

so also h needs to be indexed in your loop

final code is :

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(i)=(b-a)/i;
    s=s+2*fd(i);
    I(i)=(h(i)/2).*s;
    error(i)=I(i)-e;
    
end
      

figure(1),plot(h,error,'r')

[ataberk kaplica]

thank you its work

[Mathieu NOE]

you're welcome !

[Rik]

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).

Answer 2

[David Hill]

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));

[ataberk kaplica]

I am trying to error vs h graph for n 1-10 range