math - Solving Differential equations in Matlab, ode45 -

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i'm trying solve system 3 differential equations function ode45 in matlab. not understand errors getting , use understanding im doing wrong.

the differential equations following:

f1 = -k1y1+k2(y2-y1) f2 = -k2(y2-y1)+k3(y3-y2) f3 = -k3(y3-y2)

and code in matlab this:

function dz = kopplad(t, z) global m1 m2 m3 k1 k2 k3  dz = [z(2) -k1*z(1)/m1 + k2*(z(2)-z(1))/m1 z(4) -k2*(z(2)-z(1))+k3(z(3)-z(2))/m2 z(6) -k3(z(3)-z(2))/m3];  global m1 m2 m3 k1 k2 k3 m1 = 0.75; m2 = 0.40; m3 = 0.65; k1 = 0.85; k2 = 1.1; k3 = 2.7; [t, z] = ode45(@kopplad, [0, 50], [0 -1 0 1 0 0]); plot(t, z(:,1))  hold on plot(t,z(:,3),'--') plot(t,z(:,5),'*')  legend('y_1', 'y_2', 'y_3'); hold off

the errors i'm recieving following:

attempted access k3(1.00002); index must positive integer or logical.

error in kopplad (line 3) dz = [z(2)

error in ode45 (line 262) f(:,2) = feval(odefcn,t+ha(1),y+f*hb(:,1),odeargs{:});

error in diffekv (line 6) [t, z] = ode45(@kopplad, [0, 50], [0 -1 0 1 0 0]);

a while passed since did matlab programming, far remember, should pass variables function, i.e. write @(x,y)kopplad(x,y), if understand code in correct way. if rest (global variables , equations) correct, shall fine.


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