Split the polynomial and determine the degree of numerator and denominator

Question

sandeep singh 2019-1-23

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/441030-split-the-polynomial-and-determine-the-degree-of-numerator-and-denominator

评论： Mohsen 2019-11-6

Hello All,

I am working with some mathematical GUI , i need to split the polynomial and determine the degree of numerator and denominator . Inputs are fed from user in gui in edit text i have attached a pseudo code where i am calculating the transfer function. I need to split

OLPZData=handles.General_test.PlantInfo.OL.UDPPZForm.PZData;
    p(1)=str2double(OLPZData.p1.String);
    p(2)=str2double(OLPZData.p2.String);
    p(3)=str2double(OLPZData.p3.String);
    p(4)=str2double(OLPZData.p4.String);
    p(5)=str2double(OLPZData.p5.String);
    m=str2double(OLPZData.PolesAtOrigin.String);
    if p(1)==0 || p(2)==0 || p(3)==0 || p(4)==0 || p(5)==0
        hObject.BackgroundColor=[1 0.8 0.8];
        return;
    else
        hObject.BackgroundColor=[1 1 1];
    end
    P= sum(~isnan(p));
    if isnan(m)
        m=0;
        handles.General_test.PlantInfo.OL.UDPPZForm.PZData.PolesAtOrigin.String ='0';
        handles.General_test.PlantInfo.OL.UDPPZForm.PZData.PolesAtOrigin.BackgroundColor=[1 1 1];
    end
    z(1)=str2double(OLPZData.z1.String);
    z(2)=str2double(OLPZData.z2.String);
    z(3)=str2double(OLPZData.z3.String);
    z(4)=str2double(OLPZData.z4.String);
    z(5)=str2double(OLPZData.z5.String);
    Kdc=str2double(OLPZData.Kdc.String);
    Z= sum(~isnan(z));
    
    %Kdc(isnan(Kdc))=1;
    if isnan(Kdc)
        Kdc=1;
        handles.General_test.PlantInfo.OL.UDPPZForm.PZData.Kdc.String ='1';
        handles.General_test.PlantInfo.OL.UDPPZForm.PZData.Kdc.BackgroundColor=[1 1 1];
    end
    if z(1)==0 || z(2)==0 || z(3)==0 || z(4)==0 || z(5)==0 ||Kdc==0
        hObject.BackgroundColor=[1 0.8 0.8];
        return;
    else
        hObject.BackgroundColor=[1 1 1];
    end
	 Gvd=Kdc/((s/(2*pi))^m);
    PmultiFactor=zeros(1,5);
    ZmultiFactor=zeros(1,5);
    DENOMM=zeros(1,5);
    for i=1:5
        PmultiFactor(i)=double(~isnan(p(i)));
        ZmultiFactor(i)=double(~isnan(z(i)));
        Gvd=Gvd*(1+s*ZmultiFactor(i)/(2*pi*z(i)))/(1+s*PmultiFactor(i)/(2*pi*p(i)));
        hip = zpk(Gvd);
        hip.DisplayFormat = 'frequency';
        handles.General_test.PlantInfo.OL.PlantTF=Gvd;
        
        %PlotGeneration(hObject);
    end

extract numerator and denominator of Gvd

Thanks in advance

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Answer 1

Steven Lord 2019-1-23

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https://ww2.mathworks.cn/matlabcentral/answers/441030-split-the-polynomial-and-determine-the-degree-of-numerator-and-denominator#answer_357677

From the fact that this question is tagged "control systems" and you're calling the zpk function in your code, it sounds like you want to obtain the numerator and denominator of that transfer function. Looking at the documentation for the zpk object it has properties Z and P that contain the zeros and poles of the transfer function. You can use the poly function to create the polynomial with those roots or you could use the zp2tf function to convert your zpk object into a tf object then access that tf object's Numerator and Denominator properties.

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sandeep singh 2019-1-24

Hi Steven,

zp2tf function This is not working as my ZPK are in cell format .Any how i found the way to solve its lengthy but getting needed results.

thanks for all

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Answer 2

Walter Roberson 2019-1-23

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By definition, the degree of the denominator of a polynomial is 0 (that is, the denominator is restricted to being a constant.)

Any system in which the independent variable appears in the denominator is not a polynomial -- not even if the expression fully cancels with the numerator.

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sandeep singh 2019-1-28

Hello Walter,

I agree Transfer functions are not polynomials, but i needed to split or parse however you take . anyhow i have found solution by myself thanks for all support and replies.

Mohsen 2019-11-6