MATLAB: I am currently writing a code to plot the coordinates of a five digit airfoil, but I keep getting the error : “index exceeds matrix dimensions”. What do I do

airfoilMATLABmatrixplotting

Here is the attached code.
I would appreciate if anyone could tell me exactly what is wrong with the code and what changes I need to make to the syntax to make it run.
The error according to MATLAB:
Index exceeds matrix dimensions.
Error in NACA_23012 (line 59)
xu(i)=x(i)-yt(i)*sin(theta(i));
%this is a MATLAB program written by Akintunde Akinneye to draw the plot
%of a NACA 23012 airfoil for a university undergraduate project
clear all;
clc;
%% coder inputs
%airfoil type
typeNACA='23012';
% extrapolate values from the airfoil type using string
Linit=str2double(typeNACA(1));
Pinit=str2double(typeNACA(2));
Sinit=str2double(typeNACA(3));
Tinit=str2double(typeNACA(4:5));
%number of grid points
gridPts=500;
%constants
a0= 0.2969;
a1=-0.1260;
a2=-0.3516;
a3= 0.2843;
a4=-0.1015; % For finite thick TE
%a4=-0.1036;For zero thick TE
%% computations
% Percentage of airfoil properties in NACA number
m=0.2025;
k1=15.957;
T=Tinit/100;
%airfoil grid
x=linspace(0,1,gridPts)';
%camber and gradients
yc=ones(gridPts,1);
dyc_dx = ones(gridPts,1);
theta = ones(gridPts,1);
for i=1:1:gridPts
    if(x(i)>=0 && x(i)< m)
        yc(i)=(k1/6)*(x(i)^3-3*m*x(i)^2+m^2*(3-m)*x(i));
        dyc_dx(i)= (k1/6)*(3*x(i)^2-6*m*x(i)+ m^2*(3-m));
        
    elseif (x(i)>=m && x(i) <=1)
        yc(i)=((k1*m^3)/6) *(1-x(i));
        dyc_dx(i)= ((k1*m^3)/6);
    end
    theta(i)=atan(dyc_dx(i));
end
%thickness distro
yt=ones(gridPts,1);
for i=1:1:gridPts
    t0=a0*sqrt(x(i));
    t1=a1*x(i);
    t2=a2*x(i)^2;
    t3=a3*x(i)^3;
    t4=a4*x(i)^4;
    yt=5*T*(t0+t1+t2+t3+t4);
end
%upper surface grid
xu=ones(gridPts,1);
yu=ones(gridPts,1);
for i=1:1:gridPts
     xu(i)=x(i)-yt(i)*sin(theta(i));
    yu(i)=yc(i)+yt(i)*cos(theta(i));
end
 
%lower surface grid
xl=ones(gridPts,1);
yl=ones(gridPts,1);
for i=1:1:gridPts
    xl(i)=x(i)+yt(i)*sin(theta(i));
yl(i)=yc(i)-yt(i)*cos(theta(i));
end
%plot the airfoil shape (with lines)
f1=figure(1);
hold on; grid on;
axis equal;
plot(xu,yu,'r-');
plot(xl,yl,'k-');

Best Answer

The issue is that yt only contains one value. I suspect you may have forgotten an index on the following line:
yt=5*T*(t0+t1+t2+t3+t4);
Related Question