Replace certain elements of vector with the values from another vector

Hello!

I have 2 vectors with the same length: S_1 and S_2

I wanna substitute some values of S_1 with values of S_2 for some specific positions. For example I wanna substitute the 3d value of S_1 with the 3d value of S_2 and so on. I have saved the positions in another vector called m.

My code so far is:

syms S(t) P(t) c(t) z(t) A b g v k u d r w t Y 
eqn1 = diff(S,t) == A*(b*S)^(1-g)*(z^g) - k*z - c - b*S*(k+1);
eqn2 = diff(P,t) == u*z - d*P + (1-b)*S;
eqn3 = diff(c,t) == (((1-b)/u) * (v - A*g*(b*S)^(1-g)*z^(g-1)) + b * (A*(1-g)*b^(-g)*S^(-g)*b*z^(g) -k -1) - r) * c;
eqn4 = diff(z,t) == (((A*g*(b*S)^(1-g)*z^(g-1)-v)/(A*g*(g-1)*(b*S)^(1-g)*z^(g-2))) * (d + (((1-w)*c*u)/(w*P*(v-A*g*(b*S)^(1-g)*z^(g-1)))) + (b*(A*(1-g)*b*(b*S)^(-g)*z^g - k - 1)) + (((1-b)*(v-A*g*(b*S)^(1-g)*z^(g-1)))/u))) - (((b*A*g*b*(1-g)*(b*S)^(-g)*z^(g-1))/(A*g*(g-1)*(b*S)^(1-g)*z^(g-2))) * (A*(b*S)^(1-g)*z^g - v*z - c - b*S*(k+1)));

[VF,Subs] = odeToVectorField(eqn1,eqn2,eqn3,eqn4);
odefcn = matlabFunction(VF, 'Vars',{t,A,Y,b,d,g,k,r,u,v,w});

A=3;
b=0.4;
g=0.3;
v=2;
k=4;
u=10;
d=0.2;
r=0.5;
w=0.7;

tspan = [0 6000];
y0 = [100 60 30 50];
[t,Y] = ode45(@(t,Y) odefcn(t,A,Y,b,d,g,k,r,u,v,w) , tspan, y0);

P_1 = Y(:,1);	
S_1 = Y(:,2);
c_1 = Y(:,3);
z_1 = Y(:,4);
x_1 = b*S;

sP = size(P_1);		

MPx = (1-g)*(b*A*S_1).^(-g).*z_1.^g*b.*A;
MPz = g*(b*A*S_1).^(1-g).*z_1.^(g-1);

m = find(MPx(:,1)<MPz(:,1));
sm = size(m); 

g=0.7;
tspan2 = linspace(0, 1000, sP(1));
n0 = [100 60 30 50];   
[t,N] = ode45(@(t,N) odefcn(t,A,N,b,d,g,k,r,u,v,w) , tspan2, n0);

P_2 = N(:,1);	
S_2 = N(:,2);
c_2 = N(:,3);
z_2 = N(:,4);
x_2 = b*S;

for j=m(1):m(sm(1))
	S_1(j,1)=S_2(j,1)
end

Now for the values that MPx is smaller than MPz I wanna substitute the values of S_1 with the values of S_2. For example if MPx < MPz in the third entry then I wanna set the 3d value of S_1 to be equal to the 3d value of S_2.

Any help would be appreciated.

Thanks in advance!

[Ruben Lange]

Hi!

Could you indeed upload your entire code?

Also, could you specify which entries in the vectors S_1 and S_2 you want to change? I don't know what the criteria are...

Thanks

[Myrto Kasioumi]

I just uploaded it.

In vector m I have all the rows that I wanna substitute. I get m from the comparison between MPx and MPz. According to this comparison I am using different code. The first part uses g=0.7 and I find S_1, MPx and MPz. Then I re-run the code but for g=0.3 and I find S_2. In the end I wanna have one vector with the values of S_1 but for the specific entries that MPx<MPz I wanna substitute the values of S_1 with the values of S_2.

Thank you!

Answer 1

[Ameer Hamza]

There is no need for a for-loop

S_1(m) = S_2(m);

[Myrto Kasioumi]

Thank you.

I tried that before because I saw that someone else suggested that to some other post but still I get the following error back:

Index exceeds the number of array elements (66).

[Ameer Hamza]

The element of vector 'm' is above 281. However, there are just 66 elements in S_2. You cannot access more than 66 elements from S_2.

[Myrto Kasioumi]

Oh I see. Thank you so much