Index exceeds the number of array elements (1)

I'm getting the error as stated in the title, however I cannot determine where it comes from. Can anyone help me locate it and try and help me fix it?

% SPECIFY BOUNDARY VALUES AND NECESSARY PARAMETERS 
A=1;B=1; 
V1 = 0; V2 = 10; V3 = 20; V4 = -10;
NX = 20; %4 12 20
NY = NX;
H = A/NX;

for I = 1:NX-1
    V(I+1, 1) = V1;
    V(I+1, NY+1) = V3;
end
for J = 1:NY-1
    V(1, J+1) = V4;
    V(NX+1, J+1) = V2;
end
V(1,1) = (V1 + V4)/2.0;
V(NX+1, 1) = (V1 + V2)/2.0;
V(1, NY+1) = (V3 + V4)/2.0;
V(NX+1, NY+1) = (V2 + V3)/2.0;
%optimum
T = cos(pi/NX) + cos(pi/NY);
W = (8- sqrt(64-16*T^2))/(T^2);
disp(['SOR Factor Omega = ', num2str(W)])
W4 = W/4;
%iteration begin
NCOUNT = 0;

loop = 1;
while loop == 1;
    RMIN = 0;
    for I = 1:NX-1
        X = H*I;
        for J = 1:NY-1
            Y = H*J;
            G = -36.0*pi*X*(Y-1.0);
            R = W4*(V(I+1, J+1) + V(I, J+1) + V(I+1, J+2) + V(I+1, J) -4.0*V(I+1, J+1) - G*H*H);
            RMIN = RMIN + abs(R);
             V(I+1, J+1) = V(I+1, J+1) + R;
        end
    end
    
    RMIN = RMIN(NX*NY);
    if(RMIN >= 0.0001)
        NCOUNT = NCOUNT +1;
        if(NCOUNT >100)
            loop = 0;
            disp('Solution non convergent in 100 iterations')
        end
    else
        loop = 0;
        disp(['Solution convergent in ',num2str(NCOUNT),'iterations'])
        disp(['h = ', num2str(H)])
    end
end

Vnum = V;

%original pts through i
    abc = zeros(1,9);
    a_tic = 1;
    vec = [0:h:1];
    for ii= .25:.25:.75
        for jj = .25:.25:.75
            xind = find(vec==ii);
            yinf = find(vec==kk);
            %disp([xind, yind])
            abc(a_tic) = Vnum(xind, yind);
            a_tic = a_tic +1;
        end
    end
    
    %Output approxiamte results
    
    for I = 1:NX-1
        X = H*I;
        for J = 1:NY-1
            Y = H*J
            SUM = 0;
            for M = 1:10 %only need first 10 terms in series
                FM = M;
                for N = 1:10
                    FN = N;
                    FACTOR1 = (FM*pi/A)^2 + (FN*pi/B)^2;
                    FACTOR2 = ((-1)^(M+N))*144*A*B/(pi*FM*FN);
                    FACTOR3 = 1 - (1- (-1)^N/B);
                    FACTOR =    FACTOR2 * FACTOR3 / FACTOR1;
                    SUM = SUM + FACTOR*sin(FM*pi*X/A)*sin(FN*pi*Y/B);
                end
            end
            VH = SUM;
            
V = V';
E = gradient(V);
E = -E;
[Ex,Ey] =gradient(V);
Ex = -Ex;
Ey = -Ey;
  
x_range = (1:Nx)-mpx;
y_range = (1:Ny)-mpy;

figure(1)
contour_range_V = -130:1:130;
contour(x_range,y_range,V,contour_range_V,'linewidth',3);
axis([min(x_range) max(x_range) min(y_range) max(y_range)]);
colorbar('location','eastoutside','fontsize',14);
xlabel('x ','fontsize',14);
ylabel('y ','fontsize',14);
title('Electric Potential distribution, V in volts','fontsize',14);
h1=gca;
set(h1,'fontsize',14);
fh1 = figure(1); 
set(fh1, 'color', 'white')
xlim([0 0.1])
ylim([0 0.05])


figure(2)
contour(x_range,y_range,E,'linewidth',0.5);
hold on;
quiver(x_range,y_range,Ex,Ey,4);
axis([-10 10 -10 10]);
title('Electric field Lines, E (x,y) in V/m','fontsize',14);
colorbar('location','eastoutside','fontsize',14);
xlabel('x-axis in meters','fontsize',14);
ylabel('y-axis in meters','fontsize',14);
h2=gca;
set(h2,'fontsize',14);
fh2 = figure(2); 
set(fh2, 'color', 'white')
xlim([0 0.1])
ylim([0 0.05])            
            

Answer 1

[Star Strider]

This line is throwing the error:

RMIN = RMIN(NX*NY);

Since ‘RMIN’ is a scalar, it seems that you might be missing a multiplication (or other) operator, for example:

RMIN = RMIN*(NX*NY);

or some such.

EDIT —

There are also some end calls missing from the code you posted.

[Nicholas Gillam]

Good eye, I was missing a division sign. Thanks!

[Star Strider]

As always, my pleasure!

[Nicholas Gillam]

New update, I'm now getting an error saying "Matrix deimensions must agree". I can't see where this is happening.

[Star Strider]

You need to update the code you posted. I’m now getting:

Undefined function or variable 'h'.

in:

vec = [0:h:1];

[Nicholas Gillam]

My bad, should've posted updated code.

% SPECIFY BOUNDARY VALUES AND NECESSARY PARAMETERS 
A=1;B=1; 
V1 = 0; V2 = 10; V3 = 20; V4 = -10;
NX = 20; %4 12 20
NY = NX;
H = A/NX;

for I = 1:NX-1
    V(I+1, 1) = V1;
    V(I+1, NY+1) = V3;
end
for J = 1:NY-1
    V(1, J+1) = V4;
    V(NX+1, J+1) = V2;
end
V(1,1) = (V1 + V4)/2.0;
V(NX+1, 1) = (V1 + V2)/2.0;
V(1, NY+1) = (V3 + V4)/2.0;
V(NX+1, NY+1) = (V2 + V3)/2.0;
%optimum
T = cos(pi/NX) + cos(pi/NY);
W = (8- sqrt(64-16*T^2))/(T^2);
disp(['SOR Factor Omega = ', num2str(W)])
W4 = W/4;
%iteration begin
NCOUNT = 0;

loop = 1;
while loop == 1;
    RMIN = 0;
    for I = 1:NX-1
        X = H*I;
        for J = 1:NY-1
            Y = H*J;
            G = -36.0*pi*X*(Y-1.0);
            R = W4*(V(I+1, J+1) + V(I, J+1) + V(I+1, J+2) + V(I+1, J) -4.0*V(I+1, J+1) - G*H*H);
            RMIN = RMIN + abs(R);
             V(I+1, J+1) = V(I+1, J+1) + R;
        end
    end
    
    RMIN = RMIN/(NX*NY);
    if(RMIN >= 0.0001)
        NCOUNT = NCOUNT +1;
        if(NCOUNT >100)
            loop = 0;
            disp('Solution non convergent in 100 iterations')
        end
    else
        loop = 0;
        disp(['Solution convergent in ',num2str(NCOUNT),'iterations'])
        disp(['h = ', num2str(H)])
    end
end

Vnum = V;

%original pts through i
    abc = zeros(1,9);
    a_tic = 1;
    vec = [0:H:1];
    for ii= .25:.25:.75
        for jj = .25:.25:.75
            xind = find(vec==ii);
            yind = find(vec==jj);
            %disp([xind, yind])
            abc(a_tic) = Vnum(xind, yind);
            a_tic = a_tic +1;
        end
    end
    
    %Output approxiamte results
    
    for I = 1:NX-1
        X = H*I;
        for J = 1:NY-1
            Y = H*J
            SUM = 0;
            for M = 1:10 %only need first 10 terms in series
                FM = M;
                for N = 1:10
                    FN = N;
                    FACTOR1 = (FM*pi/A)^2 + (FN*pi/B)^2;
                    FACTOR2 = ((-1)^(M+N))*144*A*B/(pi*FM*FN);
                    FACTOR3 = 1 - (1- (-1)^N/B);
                    FACTOR =    FACTOR2 * FACTOR3 / FACTOR1;
                    SUM = SUM + FACTOR*sin(FM*pi*X/A)*sin(FN*pi*Y/B);
                end
            end
        end
    end    
            VH = SUM;
            
V = V';
E = gradient(V);
E = -E;
[Ex,Ey] =gradient(V);
Ex = -Ex;
Ey = -Ey;
  
x_range = (1:NX)-V;
y_range = (1:NY)-V;

figure(1)
contour_range_V = -130:1:130;
contour(x_range,y_range,V,contour_range_V,'linewidth',3);
axis([min(x_range) max(x_range) min(y_range) max(y_range)]);
colorbar('location','eastoutside','fontsize',14);
xlabel('x ','fontsize',14);
ylabel('y ','fontsize',14);
title('Electric Potential distribution, V in volts','fontsize',14);
h1=gca;
set(h1,'fontsize',14);
fh1 = figure(1); 
set(fh1, 'color', 'white')
xlim([0 0.1])
ylim([0 0.05])


figure(2)
contour(x_range,y_range,E,'linewidth',0.5);
hold on;
quiver(x_range,y_range,Ex,Ey,4);
axis([-10 10 -10 10]);
title('Electric field Lines, E (x,y) in V/m','fontsize',14);
colorbar('location','eastoutside','fontsize',14);
xlabel('x-axis in meters','fontsize',14);
ylabel('y-axis in meters','fontsize',14);
h2=gca;
set(h2,'fontsize',14);
fh2 = figure(2); 
set(fh2, 'color', 'white')
xlim([0 0.1])
ylim([0 0.05])            
            

[Star Strider]

Indeed they must.

Note that:

x_range = (1:NX)-V;

creates ‘(1:NX)’ as a (1 x 20) vector, and ‘V’ is a (21 x 21) matrix. If they both had one dimension in common, you could probably use the bsxfun function to do the subtraction. As it is, they are completely incompatible.

Answer 2

[James Tursa]

Type the following at the command line:

dbstop if error

Then run your code. When the error occurs, the code will pause at that line with all variables intact. Examine them to see what the size issues are, then backtrack in your code to figure out why they are not the sizes you expected.