How to use for loop when have syms inside the loop

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Hello guys,
I want to ask about, how to use for loop when I have syms and diff inside looping. Here is my code that I tried to solve. Thank you
Xmax = 1410.34;
conc = [50 100 150]*1e-9;
ka = 3.46e3;
kd = 1.46e-4;
for i = 1:length(conc)
syms t x(t)
eqn = diff(x,t) == (ka*conc(:,i)*Xmax)-(ka*conc(:,i))*x-kd*x;
cond = x(0) == 0;
X_ass(t) = dsolve(eqn,cond);
X_ass = matlabFunction(X_ass);
t = linspace(0, 1800, 600)';
signal(:,i) = [X_ass(t)];
end
When I used this code, MATLAB give me warning this:
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function
body must be sym expression.

Answers (1)

Torsten
Torsten on 30 May 2022
Try
syms t x(t)
Xmax = 1410.34;
conc = [50 100 150]*1e-9;
ka = 3.46e3;
kd = 1.46e-4;
for i = 1:length(conc)
eqn = diff(x,t) == (ka*conc(1,i)*Xmax)-(ka*conc(1,i))*x-kd*x;
cond = x(0) == 0;
X_ass(t) = dsolve(eqn,cond);
X_ass = matlabFunction(X_ass);
T = linspace(0, 1800, 600)';
signal(:,i) = X_ass(T);
end
  2 Comments
Torsten
Torsten on 31 May 2022
Try
syms t x(t) c
Xmax = 1410.34;
conc = [50 100 150]*1e-9;
ka = 3.46e3;
kd = 1.46e-4;
T = linspace(0, 1800, 600)';
eqn = diff(x,t) == (ka*c*Xmax)-(ka*c)*x-kd*x;
cond = x(0)==0;
X_ass(t) = dsolve(eqn,cond);
for i = 1:numel(conc)
X_ass_fun = matlabFunction(subs(X_ass,c,conc(i)));
signal(:,i) = X_ass_fun(T);
end

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