How do I add additional values for k into the function?

Question

johnmurdock 2019-4-25

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458604-how-do-i-add-additional-values-for-k-into-the-function

回答： Walter Roberson 2019-4-26

clear; clc; close('all');
y = 0.2;
t = 0;
h = 0.01; 
tn = 0.2;
[t, y] = Euler(t, y, h, tn);
function [t, y] = Euler(t0, y0, h, tn)
    t = (t0:h:tn)';
    y = zeros(size(t));
    y(1) = y0;
    for i = 1:1:length(t)-1
        y(i+1) = y(i) + h*f(y(i),t(i));
    end
    fprintf('The concentration of H2O after 0.2 seconds (kf=30):\n')
    disp(y(21))
end
function dydt = f(y,t)
    k1 = 30;
    c = 0.2;
    b = 0.4;
    a = 0.5;
    dydt = k1*b*a;
end

So for example, the output I have now is:

The concentration of H2O after 0.2 seconds (kf=30): 1.4000

How do I add a k2 and a k3 to the function both with values of 20 and 40 and make my output:

The concentration of H2O after 0.2 seconds (kf=30): 1.4000

The concentration of H2O after 0.2 seconds (kf=20): _______

The concentration of H2O after 0.2 seconds (kf=40): _______

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johnmurdock 2019-4-25

Thank you!

johnmurdock 2019-4-26

I understand controlling the k1 values, however I can't figure out how to impliment it all in the script file.

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Answer 1

Walter Roberson 2019-4-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/458604-how-do-i-add-additional-values-for-k-into-the-function#answer_372497

在 MATLAB Online 中打开

y = 0.2;
t = 0;
h = 0.01; 
tn = 0.2;
kf_vals = [30 20 40];
for Kidx = 1 : length(kf_vals)
    kf = kf_vals(Kidx);
    %we assume that all the t values are the same
    [t, y(:,Kidx)] = Euler(t, y, h, tn, kf);
end
for Kidx = 1 : length(kf_vals)
   kf = kf_vals(Kidx);
   fprintf('The concentration of H2O after %g seconds (kf=%g): %g\n', t(end), kf, y(end, Kidx));
 end
function [t, y] = Euler(t0, y0, h, tn, kf)
    t = (t0:h:tn)';
    y = zeros(size(t));
    y(1) = y0;
    for i = 1:1:length(t)-1
        y(i+1) = y(i) + h*f(y(i), t(i), kf);
    end
end
function dydt = f(y, t, kf)
    c = 0.2;
    b = 0.4;
    a = 0.5;
    dydt = kf*b*a;
end