Plot function for different values of two coupled variables

Hi all, I'm new to matlab so sorry if this is trivial. I'm trying to run the following code for three different values of variables k5 and k6. The thing is, I don't want a plot for every possible combination of k5 and k6. I only want three different specific combinations of k5 and k6: k5=0.1 AND k6=0.3, k5=0.2 AND k6=0.5, and k5=0.3 AND k6=0.7. So I want to run the for loop I've written for each of those three conditions. I should end up with a graph containing 6 lines (p and m vs time for each of the three conditions). I could hard code this in three different for loops but I'd rather do something nicer (unless that's not possible).

Here's the code:

k4=0.15;

a0=15;

p0=0;

m0=0;

dt=1/60;

T=60;

time=[0:dt:T];

N=length(time);

p=zeros(1,N); %placeholder output vector

p(1)=p0; %initial condition

m=zeros(1,N); %placeholder output vector

m(1)=m0; %initial condition

for n=1:N-1

dmdt=a0-k4*m(n);

dm=dmdt*dt;

m(n+1)=m(n)+dm;

dpdt=k5*m(n)-k6*p(n);

dp=dpdt*dt;

p(n+1)=p(n)+dp;

plot(time,m)

plot(time,p)

end

Answer 1

[Voss]

k4=0.15;
a0=15;
p0=0;
m0=0;
dt=1/60;
T=60;
time=0:dt:T;
N=length(time);
p=zeros(1,N); %placeholder output vector
m=zeros(1,N); %placeholder output vector

figure
hold on

all_k5 = [0.1 0.2 0.3];
all_k6 = [0.3 0.5 0.7];

for ii = 1:numel(all_k5)
    
    k5 = all_k5(ii);
    k6 = all_k6(ii);
    
    p(1)=p0; %initial condition
    m(1)=m0; %initial condition
    for n=1:N-1
        dmdt=a0-k4*m(n);
        dm=dmdt*dt;
        m(n+1)=m(n)+dm;
        dpdt=k5*m(n)-k6*p(n);
        dp=dpdt*dt;
        p(n+1)=p(n)+dp;
    end
    plot(time,m,'DisplayName',sprintf('%s [k_5=%g, k_6=%g]','m',k5,k6))
    plot(time,p,'DisplayName',sprintf('%s [k_5=%g, k_6=%g]','p',k5,k6))
    
end

legend('FontName','Courier')

The m vectors are the same for each ii, since m doesn't depend on k5 or k6. Therefore all 3 m lines coincide.

[Sophia]

this worked, thank you!!

[Voss]

You're welcome!

Answer 2

[Torsten]

k5 = [0.1 0.2 0.3];
k6 = [0.3 0.5 0.7];
colors = ['b','r','g'];
N = 3;
hold on
for i = 1:N
    [time,p,m] = fun(k5(i),k6(i));
    plot(time,[p;m],colors(i))
end
hold off
grid on

function [time,p,m] = fun(k5,k6)
  k4=0.15;
  a0=15;
  p0=0;
  m0=0;
  dt=1/60;
  T=60;
  time=[0:dt:T];
  N=length(time);
  p=zeros(1,N); %placeholder output vector
  p(1)=p0; %initial condition
  m=zeros(1,N); %placeholder output vector
  m(1)=m0; %initial condition
  for n=1:N-1
    dmdt=a0-k4*m(n);
    dm=dmdt*dt;
    m(n+1)=m(n)+dm;
    dpdt=k5*m(n)-k6*p(n);
    dp=dpdt*dt;
    p(n+1)=p(n)+dp;
    %plot(time,m)
    %plot(time,p)
  end
end

[Sophia]

this worked great, thank you so much!