MATLAB Answers

Index position 2 exceeds array bounds

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Kali Sanders
Kali Sanders on 19 Feb 2020
Answered: Hiro Yoshino on 19 Feb 2020
I am trying to run my code and I keep getting this error:
Index in position 2 exceeds array bounds.
Error in exp01_matlab (line 26)
x = A(:,1)*in2cm
Attached my code to open in matlab and I also attached my file I am using for my data
Here is my code:
clc
clear all
close all
format long
%
% Specify constants
g = 9.81; % gravity (m/s2)
mu_w = 0.001002; % water dynamic viscosity (N-s/m2)
rho_w = 998.0; % water density (kg/m3)
D_t = 0.6225*0.0254; % throat diameter (m) (based on station No.)
%
% Conversion factors
in2cm = 2.54; % inches to centimeters
in2m = 0.0254; % inches to meters
lb2newton = 4.44822; % pounds to newtons
% ---------------------------------------------------------------------------
% Import rawdata from excel
filename = 'Lab1dataSheet_Venturi_Even.xlsx'; % specify file name/directory
hRange = 'A1:I11'; % specify range of pressure data
tRange = 'K1:X5'; % specify range of flowrate data
[A,~,~] = xlsread(filename,3,hRange); % import presssure rawdata
[B,~,~] = xlsread(filename,3,tRange); % import flowrate data
%
% Sort rawdata into separate data arrays
x = A(:,1)*in2cm; THIS IS WHERE MY ERROR IS!!!!!
D = A(:,2)*in2m;
h1 = A(:,3)*in2cm;
h2 = A(:,4)*in2cm;
h3 = A(:,5)*in2cm;
h4 = A(:,6)*in2cm;
h5 = A(:,7)*in2cm;
h6 = A(:,8)*in2cm;
h1_act = h1 - h1(4);
h2_act = h2 - h2(4);
h3_act = h3 - h3(4);
h4_act = h4 - h4(4);
h5_act = h5 - h5(4);
h6_act = h6 - h6(4);
% Sort time rawdata into separate data arrays
W = B(:,2)*lb2newton;; % water weight (lbs)
t1 = B(:,3); % flow rate time in run#1 (seconds)
t2 = B(:,5); % flow rate time in run#2 (seconds)
t3 = B(:,7); % flow rate time in run#3 (seconds)
t4 = B(:,9); % flow rate time in run#4 (seconds)
t5 = B(:,11); % flow rate time in run#5 (seconds)
t6 = B(:,13); % flow rate time in run#6 (seconds)
% ----------------------------------------------------------------------------
%
% DATA PROCESSING
% ---------------------------------------------------------------------------
%
% QUESTION No. 01 - PRESSURE DISTRIBUTION
% Theoretical and actual volumetric flowrate
% Actual volumetric flowrate
V = W/(rho_w*g); % compute volume of water
a1=polyfit(t1,V,1); % fit a linear curve through data w/ polyfit
Q_act1 = a1(1); % set the slope of the curve equal to the flowrate
a2=polyfit(t2,V,1); % fit a linear curve through data w/ polyfit
Q_act2 = a2(1); % set the slope of the curve equal to the flowrate
a3=polyfit(t3,V,1); % fit a linear curve through data w/ polyfit
Q_act3 = a3(1); % set the slope of the curve equal to the flowrate
a4=polyfit(t4,V,1); % fit a linear curve through data w/ polyfit
Q_act4 = a4(1); % set the slope of the curve equal to the flowrate
a5=polyfit(t5,V,1); % fit a linear curve through data w/ polyfit
Q_act5 = a5(1); % set the slope of the curve equal to the flowrate
a6=polyfit(t6,V,1); % fit a linear curve through data w/ polyfit
Q_act6 = a6(1); % set the slope of the curve equal to the flowrate
%
% Theoretical and actual pressure distibution
Q_theo1 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h1(1)-h1(4))/(D(1)^4.-D_t^4.)); %run #1
Q_theo2 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h2(1)-h2(4))/(D(1)^4.-D_t^4.)); %run #2
Q_theo3 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h3(1)-h3(4))/(D(1)^4.-D_t^4.)); %run #3
Q_theo4 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h4(1)-h4(4))/(D(1)^4.-D_t^4.)); %run #4
Q_theo5 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h5(1)-h5(4))/(D(1)^4.-D_t^4.)); %run #5
Q_theo6 = 0.25*pi*D(1)^2.*D_t^2.*sqrt(0.02*g*(h6(1)-h6(4))/(D(1)^4.-D_t^4.)); %run #6
%With matlab for loop to calculate every theoretical height at every piezometer location (total )
for j=1:11
h1_theo(j) = (8.*Q_theo1^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #1
h2_theo(j) = (8.*Q_theo2^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #2
h3_theo(j) = (8.*Q_theo3^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #3
h4_theo(j) = (8.*Q_theo4^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #4
h5_theo(j) = (8.*Q_theo5^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #5
h6_theo(j) = (8.*Q_theo6^2.)/(pi^2.*g)*(1./D_t^4. - 1./D(j)^4.)*100.; % (cm) run #6
end
%
% QUESTION No. 02 - DISCHARGE COEFFICIENT
% Discharge coefficient and Reynolds number
Rd=zeros(6,1) %initialize vector for Roynold number list
Cd=zeros(6,1) %initialize vector for discharge coefficient list
Cd(1) = Q_act1/Q_theo1; % discharge coefficient
Re(1) = 4.*rho_w*Q_act1/(pi*mu_w*D_t); % reynolds number
Cd(2) = Q_act2/Q_theo2; % discharge coefficient
Re(2) = 4.*rho_w*Q_act2/(pi*mu_w*D_t); % reynolds number
Cd(3) = Q_act3/Q_theo3; % discharge coefficient
Re(3) = 4.*rho_w*Q_act3/(pi*mu_w*D_t); % reynolds number
Cd(4) = Q_act4/Q_theo4; % discharge coefficient
Re(4) = 4.*rho_w*Q_act4/(pi*mu_w*D_t); % reynolds number
Cd(5) = Q_act5/Q_theo5; % discharge coefficient
Re(5) = 4.*rho_w*Q_act5/(pi*mu_w*D_t); % reynolds number
Cd(6) = Q_act6/Q_theo6; % discharge coefficient
Re(6) = 4.*rho_w*Q_act6/(pi*mu_w*D_t); % reynolds number
%
% %
% QUESTION No. 03 - HEAD LOSS
% Head loss
H_T (1) = h1(1) - h1(11);
H_T (2) = h2(1) - h2(11);
H_T (3) = h3(1) - h3(11);
H_T (4) = h4(1) - h4(11);
H_T (5) = h5(1) - h5(11);
H_T (6) = h6(1) - h6(11);
Q_act = [Q_act1,Q_act2,Q_act3,Q_act4,Q_act5,Q_act6]
% %
% ----------------------------------------------------------------------------
%
% OUTPUT PLOTS FOR DATA REDUCTION
% ---------------------------------------------------------------------------
%
% QUESTION No. 01 - PRESSURE DISTRIBUTION
%plot actual pressure vs. x location of piezometers.
figure(1);
plot(x,h1_act,'ro', x,h2_act,'yo', x,h3_act,'bo', x,h4_act,'co', x,h5_act,'mo', x,h6_act,'ko');
hold on
%plot theoretical pressure vs. x location of piezometers.
plot(x,h1_theo,'r--', x,h2_theo,'y--', x,h3_theo,'b--', x,h4_theo,'c--', x,h5_theo,'m--', x,h6_theo,'k--');
hold off
xlabel('Axial position (cm)')
ylabel('Pressure head (cm of H_2O)')
legend('10 in H_2O','8 in H_2O','6 in H_2O', '4 in H_2O', '2 in H_2O','0.6 in H_2O');
%
% QUESTION No. 02 - DISCHARGE COEFFICIENT
figure(2);
plot(Re/10000,Cd,'bo-')
xlabel('Reynolds number \times10^4')
ylabel('Discharge coefficient') % %
% %
% % QUESTION No. 03 - HEAD LOSS
%QUESTION No. 03 - HEAD LOSS
figure(3);
plot(Q_act*10000,H_T,'bo-')
xlabel('Volumetric flow-rate \times10^2 (cm^3/s)')
ylabel('Head loss (cm of H_2O)')
% ----------------------------------------------------------------------------
%
% END OF FILE
% ----------------------------------------------------

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Accepted Answer

Hiro Yoshino
Hiro Yoshino on 19 Feb 2020
I had a look at it quickly - you were obviously failing in importing the pressure and the flowrate.
xlsread(filename, 3, hRange)
there are just images on the 3rd sheet; there are no numbers to be imported.
You should change to either, I guess, 1 or 2, which I've tried.
However you are still having a problem which is associated with the matrix B.
I guesss the way you specified the hRange, and tRange was not correct.
You should modify them appropriately.

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