I am having trouble multiplying my main ode function with an external function NS which is supposed to be multiplied on the RHS. Thanks for the great help.

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Dereje
Dereje 2017-11-30
评论： Dereje 2017-12-1
tspan = [0 20];
y0 = [0 0.01];
[z,y] = ode45(@odefcn, tspan, y0);
plot(z,y(:,1),'-o',z,y(:,2),'-.')
function dydt = odefcn(z,y)
dydt1 = y(2);
dydt2 = NS*z.*y(1);
dydt=[dydt1;dydt2];
end
function M = NS(z)
z = [2 3 5 7 10 15 20 ];
r =[3.5 3.7 4 6 7.2 8 9];
n=length(z);
% Calculation of differentiation from the above datas
for i=1:n-1
M=zeros();
M(i)=(r(i+1)-r(i))./(z(i+1)-z(i));
end
end
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Dereje
Dereje 2017-11-30
I wanted to solve a function with the name odefcn. But my problem is the RHS is supposed to be multiplied with external function which is differentiation of data points.

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Torsten
Torsten 2017-11-30
zr = [2 3 5 7 10 15 20];
r = [3.5 3.7 4 6 7.2 8 9];
y0 = [0 ; 0.01];
zsol = [];
y1sol = [];
y2sol = [];
for i=1:numel(r)-1
zspan = [zr(i) zr(i+1)];
NS = (r(i+1)-r(i))/(zr(i+1)-zr(i));
[z,y] = ode45(@(z,y)odefcn(z,y,NS), zspan, y0);
y0 = [y(end,1) ; y(end,2)];
zsol = [zsol;z];
y1sol = [y1sol;y(:,1)];
y2sol = [y2sol;y(:,2)];
end
plot(zsol,y1sol,zsol,y2sol)
function dydt = odefcn(z,y,NS)
dydt1 = y(2);
dydt2 = NS*z*y(1);
dydt=[dydt1;dydt2];
end
Best wishes
Torsten.
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