How to create nested for loops that has two changing variables to output one variable?

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Alyssa Mills 2018-12-4

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https://ww2.mathworks.cn/matlabcentral/answers/433655-how-to-create-nested-for-loops-that-has-two-changing-variables-to-output-one-variable

评论： Alyssa Mills 2018-12-4

This is the code I am trying to run, and I am unsure how to write nested for loops to run over a certain time period and length.

Context: I am trying to find what the function will look like after the time ends and how r and hz evolve. Ultimately I will want to plot the r and hz together.

%Intial Conditions
rho=(3.6*30*24*60*60); %3.6 months
u=10^9;
u0=2*10^-5; 
v=1*10^6;
r0=2000; %Intial radius
h0=180; %Intial height
V=(3/4)*pi()*(r0^2)*h0; %volume
v0=1*10^6;
g=1.31;
tau=((3/4)^5)*(((pi()^3)*v0*(r0^8))/(g*V^3));
%% Theta 
for t=1:172800; %Using the time for 2 days
    theta(t)=rho*(1-exp(-t/rho));
end
%% Solving function  
for r=1:3000;
    for ta=1:theta;
        hz(r,ta)=(((4*V)/(3*pi()*r0^2)).*(1./((1+(ta./tau)).^1/4)).*(1-(((r.^2)./(r0^2)).*(1./(1+((ta./tau).^1/4))))).^(1/3));
    end
end

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Alyssa Mills 2018-12-4

I'm trying to find height as a function of radius. Here is the equation I am trying to use where I eventually want to test different times (t) and radii (r). Screen Shot 2018-12-03 at 9.48.16 PM.png

Screen Shot 2018-12-03 at 9.48.16 PM.png

Walter Roberson 2018-12-4

Your code already tests different angles (ta) and different radii (r ) . If you want to test different tau as well you would add another loop and probably add another index on the output.

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采纳的回答

Walter Roberson 2018-12-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/433655-how-to-create-nested-for-loops-that-has-two-changing-variables-to-output-one-variable#answer_350373

在 MATLAB Online 中打开

rho=(3.6*30*24*60*60); %3.6 months
u=10^9;
u0=2*10^-5; 
v=1*10^6;
r0=2000; %Intial radius
h0=180; %Intial height
V=(3/4)*pi()*(r0^2)*h0; %volume
v0=1*10^6;
g=1.31;
tau=((3/4)^5)*(((pi()^3)*v0*(r0^8))/(g*V^3));
%% Theta 
for t=1:172800; %Using the time for 2 days
    theta(t)=rho*(1-exp(-t/rho));
end
%% Solving function
hz = zeros(3000, length(theta));
for r=1:3000;
    for ta=1:length(theta);
        hz(r,ta)=(((4*V)/(3*pi()*r0^2)).*(1./((1+(theta(ta)./tau)).^1/4)).*(1-(((r.^2)./(r0^2)).*(1./(1+((theta(ta)./tau).^1/4))))).^(1/3));
    end
end

This is rather slow and you should try to vectorize it.

Thank you so much for the help! You helped vectorize which I am sort of familiar with but couldn't get it exactly down. I'll try to play with this to make the curves match exactly to the previous plot. I had gotten the exact curve of t=2 days previously (using the conditions I have above), but I sadly didn't save that script.

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