Running a loop to generate multiple graphs using the same equation with different parameters

Hi All,

Below represents a model for exponential growth or decay. Any help much appreciated.

clear all; clc

t=linspace(0,5);

a=.75;

b=1;

c=1.5;

R0=1

R=R0*exp(a*t);

R1=R0*exp(b*t);

R2=R0*exp(c*t);

subplot(2,2,1)

xlabel('R(t)');

ylabel('Time');

plot(t, R,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R1,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R2,'g--'), title('Solution to dR/dt with R0>0');

hold on

xlim([0 5])

ylim([0 100])

hold off

grid;

I would like to figure out how to run a loop so that I can run both the variables for the equation and also a,b and c. The reason is because I want to add more plots like I have done below, but that is becoming inefficient. Any help much appreciated.

Final result should look like this but with a loop for R and also a, b and c.

clear all; clc

t=linspace(0,5);

a=.75;

b=1;

c=1.5;

d=-.5;

e=-1;

f=-2;

R0=1;

Ra=-1;

Rb=100;

Rc=-100;

R=R0*exp(a*t);

R1=R0*exp(b*t);

R2=R0*exp(c*t);

subplot(2,2,1)

xlabel('R(t)');

ylabel('Time');

plot(t, R,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R1,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R2,'g--'), title('Solution to dR/dt with R0>0');

hold on

xlim([0 5])

ylim([0 100])

hold off

grid;

R3=Ra*exp(a*t);

R4=Ra*exp(b*t);

R5=Ra*exp(c*t);

subplot(2,2,2)

xlabel('R(t)');

ylabel('Time');

plot(t, R3,'g--'), title('Solution to dR/dt with R0<0');

hold on

plot(t, R4,'g--'), title('Solution to dR/dt with R0<0');

hold on

plot(t, R5,'g--'), title('Solution to dR/dt with R0<0');

hold on

xlim([0 5])

ylim([-100 0])

hold off

grid;

R6=Rb*exp(d*t);

R7=Rb*exp(e*t);

R8=Rb*exp(f*t);

subplot(2,2,3)

xlabel('R(t)');

ylabel('Time');

plot(t, R6,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R7,'g--'), title('Solution to dR/dt with R0>0');

hold on

plot(t, R8,'g--'), title('Solution to dR/dt with R0>0');

hold on

xlim([0 5])

ylim([0 100])

hold off

grid;

R9=Rc*exp(d*t);

R10=Rc*exp(e*t);

R11=Rc*exp(f*t);

subplot(2,2,4)

xlabel('R(t)');

ylabel('Time');

plot(t, R9,'g--'), title('Solution to dR/dt with R0<0');

hold on

plot(t, R10,'g--'), title('Solution to dR/dt with R0<0');

hold on

plot(t, R11,'g--'), title('Solution to dR/dt with R0<0');

hold on

xlim([0 5])

ylim([-100 0])

hold off

grid;

However I am unhappy with the constant reuse of a, b, c, and the reuse of the equations

Any help much appreciated.

Answer 1

[Mathieu NOE]

hello

yes your code could be made more compact and flexible

see my suggestion below

clc
clearvars

t = linspace(0,5);

% organize aa = [a b c]' as a array of 4 columns corresponding to the 4
% scenarios   (subplots) 
aa =    [.75 .75 -.5 -.5;   % formerly a
        1 1 -1 -1;          % formerly b
        1.5 1.5 -2 -2];     % formerly c
    
% organize R0 as a array of 4 columns corresponding to the 4 scenarios  (subplots) 
R0 = [1 -1 100 -100];
[m,n] = size(aa);

figure(1);
for ci = 1:n % number of scenarios  (subplots) 
    for ck = 1:m % number of curves per scenario (subplots) 
        R(ck,:)=R0(ci)*exp(aa(ck,ci)*t);
    end
    subplot(2,2,ci)
    plot(t, R,'g--'),grid on;
    xlabel('R(t)');
    ylabel('Time');
    xlim([0 5]);
    if R(1,1) <0
        ylim([-100 0])
    else
        ylim([0 100])
    end
end

[Kevin Holly]

I had a similar thought process.

clear all; clc
t=linspace(0,5);
%Inputs
a=[.75 1 1.5; -.5 -1 -2];
R=[1 -1 100 -100];
titles = ["Solution to dR/dt with R0>0" "Solution to dR/dt with R0<0"];

for j = 1:4
    %Plots
    nexttile %I used nexttile in case you wanted to add more scenarios
    for i = 1:3
        plot(t, R(j)*exp(a(ceil(j/2),i)*t),'g--')
        hold on
    end
    title(titles(ceil(j/2)))
    xlabel('R(t)');
    ylabel('Time');
    xlim([0 5])
    if rem(j,2) == 0
        ylim([-100 0])
    else
        ylim([0 100])
    end
    hold off
    grid;
end

[See Goo]

Thank you!

These are much more compact and exactly what I was after.

Kind regards,