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How to use fminsearch for my code

Asked by Saeid Bina on 11 Nov 2019 at 3:16
Latest activity Commented on by Saeid Bina on 11 Nov 2019 at 6:06
Hello everyone, I am new in MATLAB. Please help me find out my problem.
I prepared a code that aimed at finding parameters to fit the data. (data is recorded temperature vs. time)
it is work by changing that three parameters manually but I would like to use fminsearch but always faild!
Thanks in advance.
here is my code (the objective is RMSE):
close all, clear all, clc
load GHE1_6kW_P12_V1.txt
[min,n]=size(GHE1_6kW_P12_V1);
tau = GHE1_6kW_P12_V1(240:end,1);
Tfm_mis = GHE1_6kW_P12_V1(240:end,2);
rho_s = 2533; %[kg/mc]
c_s = 840; %[J/kg.K]
eps = 0.4;
T_0 = 15.96;
rho_w = 1020; %water density [kg/mc]
c_w = 4186;
r_bh= 0.076; %borehole ID/OD=151/165
q = 110.22; %[W/m]
a_s = 0.25;
par=[10,1.7E-6,0.09];
C_0 = rho_s*c_s*(1-eps)+rho_w*c_w*eps;
est = r_bh^2*C_0/4*tau*par(1);
f=(1./est).*exp((-1./est)-((par(2)^2)*c_w^2*r_bh^2*rho_w^2)/16*par(1));
T=cumtrapz(est,f);
dteta= 45*pi/180;
teta =(dteta : dteta : 2*pi);
for j=1:numel(teta)
z(1,j)= q/(4*pi*par(1))*exp((par(2)*rho_w*c_w*r_bh*cos(teta(j)))/2*par(1));
end
g=T*z;
A=mean(g');
B = T_0+A;
Tfm_MLS= B + (q * par(3));
plot(Tfm_MLS,'r')
hold on
plot (Tfm_mis,'g')
RMSE = (sum((Tfm_MLS-Tfm_mis).^2)/length(tau)).^0.5;

  1 Comment

Walter Roberson
on 11 Nov 2019 at 4:05
Which variables need to be optimized over? Is it the par vector?
Is RMSE the equation whose value is to be minimized? \
Is there a reason you are using a loop for
for j=1:numel(teta)
z(1,j)= q/(4*pi*par(1))*exp((par(2)*rho_w*c_w*r_bh*cos(teta(j)))/2*par(1));
end
instead of
z = q./(4*pi*par(1)).*exp((par(2).*rho_w.*c_w.*r_bh.*cos(teta))./2.*par(1));
which is vectorized?

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1 Answer

Answer by Saeid Bina on 11 Nov 2019 at 4:10

Yes Par need to be optimaized and while RMSE is minimized. RMSE is the diffrence between calculated and measured data.
I have used loop beacuase that fuction need to be calculated for 8 teta. It is kind a 3D matrix. The data are calculating for timly basis and at each min for 8 teta (degree) and then using Mean for finding average temperature for each min.
by the way if you think is not needed, your idea is respected.

  2 Comments

Walter Roberson
on 11 Nov 2019 at 5:48
Vectorizing that loop that calculates z would be more efficient.
Make sure, though, that you use ./ and .* instead of / and * like I show in my code.
Saeid Bina on 11 Nov 2019 at 6:06
Yes, I have used that one, it results in same. Please help me to optimaize par.

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