help with nested loops

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

Answer 1

[Star Strider]

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.

.

Answer 2

[Voss]

"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)