Polynomial is badly conditioned
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From: Saga on 4 Mar 2010 09:12 Guys trying to create a polynomial formula but I go above order 5 i get this error msg "Warning: Polynomial is badly conditioned. Add points with distinct X values, reduce the degree of the polynomial, or try centering and scaling as described in HELP POLYFIT." I've looked at help, but there is no information there. Thanks
From: Steven Lord on 4 Mar 2010 09:36 "Saga " <a5stargamescompany(a)googlemail.com> wrote in message news:hmof3l$851$1(a)fred.mathworks.com... > Guys trying to create a polynomial formula but I go above order 5 i get > this error msg "Warning: Polynomial is badly conditioned. Add points with > distinct X > values, reduce the degree of the polynomial, or try centering > and scaling as described in HELP POLYFIT." > > I've looked at help, but there is no information there. Reread this section from the help: [P,S,MU] = POLYFIT(X,Y,N) finds the coefficients of a polynomial in XHAT = (X-MU(1))/MU(2) where MU(1) = MEAN(X) and MU(2) = STD(X). This centering and scaling transformation improves the numerical properties of both the polynomial and the fitting algorithm. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
From: Saga on 4 Mar 2010 09:48 "Steven Lord" <slord(a)mathworks.com> wrote in message <hmoggi$as7$1(a)fred.mathworks.com>... > > "Saga " <a5stargamescompany(a)googlemail.com> wrote in message > news:hmof3l$851$1(a)fred.mathworks.com... > > Guys trying to create a polynomial formula but I go above order 5 i get > > this error msg "Warning: Polynomial is badly conditioned. Add points with > > distinct X > > values, reduce the degree of the polynomial, or try centering > > and scaling as described in HELP POLYFIT." > > > > I've looked at help, but there is no information there. > > Reread this section from the help: > > [P,S,MU] = POLYFIT(X,Y,N) finds the coefficients of a polynomial in > XHAT = (X-MU(1))/MU(2) where MU(1) = MEAN(X) and MU(2) = STD(X). This > centering and scaling transformation improves the numerical properties > of both the polynomial and the fitting algorithm. > > -- > Steve Lord > slord(a)mathworks.com > comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ > OK I understand it, but have no idea how to apply the method? Thanks
From: Steven Lord on 4 Mar 2010 10:15 "Saga " <a5stargamescompany(a)googlemail.com> wrote in message news:hmoh72$qvk$1(a)fred.mathworks.com... > "Steven Lord" <slord(a)mathworks.com> wrote in message > <hmoggi$as7$1(a)fred.mathworks.com>... >> >> "Saga " <a5stargamescompany(a)googlemail.com> wrote in message >> news:hmof3l$851$1(a)fred.mathworks.com... >> > Guys trying to create a polynomial formula but I go above order 5 i get >> > this error msg "Warning: Polynomial is badly conditioned. Add points >> > with distinct X >> > values, reduce the degree of the polynomial, or try centering >> > and scaling as described in HELP POLYFIT." >> > >> > I've looked at help, but there is no information there. >> >> Reread this section from the help: >> >> [P,S,MU] = POLYFIT(X,Y,N) finds the coefficients of a polynomial in >> XHAT = (X-MU(1))/MU(2) where MU(1) = MEAN(X) and MU(2) = STD(X). This >> centering and scaling transformation improves the numerical >> properties >> of both the polynomial and the fitting algorithm. >> >> -- >> Steve Lord >> slord(a)mathworks.com >> comp.soft-sys.matlab (CSSM) FAQ: >> http://matlabwiki.mathworks.com/MATLAB_FAQ > > OK I understand it, but have no idea how to apply the method? > > Thanks > Call the function with three outputs. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
From: Saga on 4 Mar 2010 17:24 "Steven Lord" <slord(a)mathworks.com> wrote in message <hmoipk$av0$1(a)fred.mathworks.com>... > > "Saga " <a5stargamescompany(a)googlemail.com> wrote in message > news:hmoh72$qvk$1(a)fred.mathworks.com... > > "Steven Lord" <slord(a)mathworks.com> wrote in message > > <hmoggi$as7$1(a)fred.mathworks.com>... > >> > >> "Saga " <a5stargamescompany(a)googlemail.com> wrote in message > >> news:hmof3l$851$1(a)fred.mathworks.com... > >> > Guys trying to create a polynomial formula but I go above order 5 i get > >> > this error msg "Warning: Polynomial is badly conditioned. Add points > >> > with distinct X > >> > values, reduce the degree of the polynomial, or try centering > >> > and scaling as described in HELP POLYFIT." > >> > > >> > I've looked at help, but there is no information there. > >> > >> Reread this section from the help: > >> > >> [P,S,MU] = POLYFIT(X,Y,N) finds the coefficients of a polynomial in > >> XHAT = (X-MU(1))/MU(2) where MU(1) = MEAN(X) and MU(2) = STD(X). This > >> centering and scaling transformation improves the numerical > >> properties > >> of both the polynomial and the fitting algorithm. > >> > >> -- > >> Steve Lord > >> slord(a)mathworks.com > >> comp.soft-sys.matlab (CSSM) FAQ: > >> http://matlabwiki.mathworks.com/MATLAB_FAQ > > > > OK I understand it, but have no idea how to apply the method? > > > > Thanks > > > > Call the function with three outputs. > > -- > Steve Lord > slord(a)mathworks.com > comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ > Three outputs??? I only have (x,y,n) The higher order I go it display the error. Do you mean like this? [P,S,MU] = POLYFIT(X,Y,N) If yes what values are P,S and MU? Thanks
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