I'm getting an error using: ver_4/singleButtonPushed The index in position 1 is invalid. Array indices must be positive integers or logical values.

function [vector] = SUBPIX2DGAUSS (result_conv,interrogationarea,x,y,SubPixOffset)

if (x <= (size(result_conv,1)-1)) && (y <= (size(result_conv,1)-1)) && (x >= 1) && (y >= 1)

c10=zeros(3,3);

c01=c10;

c11=c10;

c20=c10;

c02=c10;

for i=-1:1

for j=-1:1

if i ~= 0

c10(j+2,i+2)=i*log(result_conv(y+j, x+i)); % It says that the index is invalid in this part

c11(j+2,i+2)=i*j*log(result_conv(y+j, x+i));

end

if j~=0

c01(j+2,i+2)=j*log(result_conv(y+j, x+i));

end

c20(j+2,i+2)=(3*i^2-2)*log(result_conv(y+j, x+i));

c02(j+2,i+2)=(3*j^2-2)*log(result_conv(y+j, x+i));

end

end

c10=(1/6)*sum(sum(c10));

c01=(1/6)*sum(sum(c01));

c11=(1/4)*sum(sum(c11));

c20=(1/6)*sum(sum(c20));

c02=(1/6)*sum(sum(c02));

temp=4*c20*c02-c11^2;

deltax=(c11*c01-2*c10*c02)/temp;

deltay=(c11*c10-2*c01*c20)/temp;

peakx=x+deltax;

peaky=y+deltay;

SubpixelX=peakx-SubPixOffset;

SubpixelY=peaky-SubPixOffset;

vector=[SubpixelX, SubpixelY];

else

vector=[NaN NaN];

end

end

Answer 1

[Voss]

Suppose result_conv is of size 2-by-2 and x is 1 and y is 1. Then all the if conditions are met, so the for loops are executed. Then the first iteration of the inner loop has i=-1 and j=-1, so y+j=0 and x+i=0. That means the code will try to access result_conv(0,0), which is in error because indexing starts with 1 in MATLAB.

% Suppose result_conv is of size 2-by-2 and x is 1 and y is 1
if (x <= (size(result_conv,1)-1)) ...         % 1 <= 1
        && (y <= (size(result_conv,1)-1)) ... % 1 <= 1
        && (x >= 1) ...                       % 1 >= 1
        && (y >= 1)                           % 1 >= 1
    % ...
    for i=-1:1
        for j=-1:1
            if i ~= 0
                % the first time here, i=-1 and j=-1, so
                % y+j=0 and x+i=0, so result_conv(y+j,x+i) is
                % result_conv(0,0), an error
                c10(j+2,i+2)=i*log(result_conv(y+j, x+i));
                % ...
            end
            % ...
        end
    end
end

Perhaps the 3rd and 4th conditions in the if statement should be x >= 2 && y >= 2?

Or equivalently, if x and y are always integers (which they should be since they're being used for indexing), perhaps this is more clear:

if x < size(result_conv,1) ...
        && y < size(result_conv,1) ...
        && x > 1 ...
        && y > 1