Differential Equations and Variables

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J 2013-4-10

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https://ww2.mathworks.cn/matlabcentral/answers/71406-differential-equations-and-variables

Hello,

I would like to know if it's possible to execute and store results from a simple linear differential equation pulling one of the variable from an external file and storing/saving the results in a different file keeping the same formatting.

To better explain, here is what I am trying to do:

I have a table in excel, column 'I' is one of the variable in my model where values change. I need to compute the results of my differential equation so that the result can be inserted next to each of the cells of 'I'

'I' is the variable which would actually vary in my case

my diff equations is: dx/dt=I(S+A).

Thank you regards J

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采纳的回答

Yao Li 2013-4-10

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https://ww2.mathworks.cn/matlabcentral/answers/71406-differential-equations-and-variables#answer_81688

在 MATLAB Online 中打开

I=xlsread('Path\filename.xlsx','I:I');
%add your own codes to solve the equation
n=length(I);
range=strcat('J1:J',num2str(n));
xlswrite('Path\filename.xlsx',output,range);

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Yao Li 2013-4-10

编辑：Yao Li 2013-4-10

在 MATLAB Online 中打开

Assuming I, S and A are stored in columns A,B and C, respectively. The results x will be stored in column D. Hope the codes below can help:

    data=xlsread('Path\filename.xlsx','A:C');
    I=data(:,1);
    S=data(:,2);
    A=data(:,3);
    time=(30:30:48*60)';  
    n=length(time);
    range=strcat('D1:D',num2str(n));
    x0=1;
    x(1)=x0;
    for i=2:1:n
    c(i)=trapz(time(1:i),(I(1:i).*(S(1:i)+A(1:i))));
    x(i)=x0*exp(c(i));
    end
    xlswrite('Path\filename.xlsx',x',range);