help with nested loops

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Corey
Corey 2025-3-13
回答： Voss 2025-3-13
Hi all, I know I am not quite getting this right but I am trying to run a nested loop that will output an array of temperatures for every eps value. If I fix the eps value the script will run fine over the range of temperatures but I would like to save time and be able to vary temperature and eps. Any help would be greatly appreciated. Do I need to pre allocate zero arrays with as many rows as there are eps values?
%range of temperatures
Texplore=[0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1400 1600 1800 2000];
epsexplore=[1e-7 1e-8 1e-9 1e-10 1e-11];
%pre allocate stress array
pl=zeros(17,1);
qz=zeros(17,1);
plD=zeros(17,1);
%solve for stress
for i=1:length(Texplore)
Tuse=Texplore(i);
for j=length(epsexplore)
epsuse=epsexplore(j);
pl(i,j)=((epsuse)/(A*exp(-Q/(R*Tuse))))^(1/n);
qz(i,j)=((epsuse)/(A1*exp(-Q1/(R*Tuse))))^(1/n1);
plD(i,j)=((epsuse)/(A2*exp(-Q2/(R*Tuse))))^(1/n);
end
end

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回答（2 个）

Star Strider
Star Strider 2025-3-13
Ran in:
You don’t actually need nested loops (or for that matter, any loops) to calculate those in MATLAB.
Texplore=[0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1400 1600 1800 2000];
epsexplore=[1e-7 1e-8 1e-9 1e-10 1e-11];
[Tuse,epsuse] = ndgrid(Texplore, epsexplore);
A = rand
A = 0.4526
A1 = rand
A1 = 0.0116
A2 = rand
A2 = 0.8720
Q = rand
Q = 0.9927
Q1 = rand
Q1 = 0.8255
Q2 = rand
Q2 = 0.7760
R = rand
R = 0.7689
n = randi(10)
n = 10
n1 = randi(10)
n1 = 2
pl = ((epsuse)./(A*exp(-Q./(R*Tuse)))).^(1/n);
qz = ((epsuse)./(A1*exp(-Q1./(R*Tuse)))).^(1/n1);
plD = ((epsuse)./(A2*exp(-Q2./(R*Tuse)))).^(1/n);
figure
surf(Tuse,epsuse,pl)
grid on
colormap(turbo)
figure
surf(Tuse,epsuse,qz)
grid on
colormap(turbo)
figure
surf(Tuse,epsuse,plD)
grid on
colormap(turbo)
This aproach uses vectorization and element-wise division and exponentiation.
.
Voss
Voss 2025-3-13
"If I fix the eps value the script will run fine over the range of temperatures but I would like to save time and be able to vary temperature and eps."
The problem is that instead of
for j=length(epsexplore)
you need
for j=1:length(epsexplore)

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