Can you help me with this line of code that I am missing? I need it to also show the level of error

Greenhorn

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posted 1 month ago

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Hello, I need help with this code in matlab. This is Hermite interpolation, in which the polynomial obtained in point 1.03 is approximated, then the real error and the error bound are calculated. The detail is that I have not been able to calculate the Lagrange error bound. Can you help me with this line of code that I am missing? I need it to also show the level of error committed

%------------------------------- -------------------
función P = HPoly(x,y,yp)
    n = longitud(x);
    para k=1:(2*n)
        Bx(:,k)=x'.^(k-1) ;
    final
    Bp(:,1)=ceros(n,1) ;
    para k=2:(2*n)
        Bp(:,k)=(k-1)*x'.^(k-2) ;
    final
    P = flip([Bx;Bp]\[y,yp]')';
fin
%------------------------------------------------ --
función y = f(x)
    y = 3*x.*exp(x)-exp(2*x) ; función
final
y = fp(x)
    y = 3*exp(x).*(x + 1) - 2*exp(2*x);
fin
%------------------------------------------------ --
% GRADO 3
%
x = [1, 1.05] ;
y = f(x);
yp = fp(x);

xprueba = 1,03;
%------------------------------------------------- -

P = HPoly(x,y,yp);
Err3 = polival(P,xtest) - f(xtest)
función Lagrange_error_bound = max(abs((xtest-x(1))*(xtest-x(2)))*(abs(fp(t))/(2 *factorial(3))), abs((xtest-x(1))*(xtest-x(2))*(xtest-x(3)))*(abs(fp(t))/(6* factorial(4))));
  final
xb = [1:.001:1.05];
yb = f(xb) ;
H = polival(P,xb);

subtrama(2,2,1);trama(xb,yb,"r",xb,H,"g",x,y,"r*")
subtrama(2,2,2);trama(xb,H -yb,xtest,Err3,"r*")

%------------------------------------- -------------

% GRADO 5
%
x = [1, 1.05, 1.07] ;
y = f(x);
yp = fp(x);

xprueba = 1,03;
%------------------------------------------------- -

P = HPoly(x,y,yp);
Err5 = polival(P,xtest) - f(xtest)

xb = [1:.001:1.07];
yb = f(xb) ;
H = polival(P,xb);

subtrama(2,2,3);trama(xb,yb,"r",xb,H,"g",x,y,"r*")
subtrama(2,2,4);trama(xb,H -yb,xtest,Err5,"r*")
%------------------------------------- -------------

Stephan van Hulst

Saloon Keeper

Posts: 15621

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posted 1 month ago

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Welcome CodeRanch!

It's been a looooong time since I have coded in MatLab. I'm not sure I'll be able to help you right away.

One thing that stands out to me is that you define xprueba, but don't appear to use it. Was that your intention?

Isabel Zambrano

Greenhorn

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posted 1 month ago

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Hello, thanks for answering. That is not my intention, xproba should calculate the approximation to 1.03 of the polynomial obtained, however it does not do so. Just like the error level, it does not execute that part either. I need you to give me the error rate

Don't get me started about those stupid light bulbs.