Index in position 1 is invalid. Array indices must be positive integers or logical values.

Hello everyone, I am trying to get edge detected images from the code below but it keeps telling the same error which is :

Index in position 1 is invalid. Array indices must be positive integers or logical values.

Error in

elseif ( IF(i+1,j)<0 || IF(i-1,j)<0 || IF(i,j+1)<0 || IF(i,j-1)<0 || IF(i-1, j-1)<0 || IF(i-1, j+1)<0 || IF(i+1,

j+1)<0 || IF(i+1, j-1)<0)

Please could anyone help me resolving the problem, thank you!

close all;
clc;
%Input image
inim = imread ('ruins.jpg');
inimg = rgb2gray(inim);
%Value for Thresholding
T_Low = 0.075;
T_High = 0.175;
k = 2;
delta_t = 0.1;
col=size(inimg,1);
row=size(inimg,2);
cC = ((abs(inimg)).^2)./(1 + ((abs(inimg).^2).*delta_t)).^k;
F = fft(inimg);
J = cC .* F;
IF1 = ifft(J);
IF = real(IF1);
%Hysteresis Thresholding
T_Low = T_Low * max(max(IF));
T_High = T_High * max(max(IF));
T_res = zeros (pan, leb);
for i = 1  : col
    for j = 1 : row
        if (IF(i, j) < T_Low) 
            T_res(i, j) = 0;
        elseif(IF(i, j) > T_High) 
            T_res(i, j) = 1;
        %look for the negative in 8-connected components
        elseif ( IF(i+1,j)<0 || IF(i-1,j)<0 || IF(i,j+1)<0 || IF(i,j-1)<0 || IF(i-1, j-1)<0 || IF(i-1, j+1)<0 || IF(i+1, j+1)<0 || IF(i+1, j-1)<0)
            T_res(i,j) = 1;
        end
    end
end

Answer 1

[KALYAN ACHARJYA]

( IF(i+1,j)<0 || IF(i-1,j)<0 || IF(i,j+1)<0 || IF(i,j-1)<0 || IF(i-1, j-1)<0 || IF(i-1, j+1)<0 || 
%......^.............^................^............^...so on
When i=1.............^^ becomes zero that menas IF(i-1,j)>>IF(0,j)
When j=1............................................^^ >>IF(i,0)

These array indeces must be non zero positive integer.

IF (0,2)>>  not allowed
IF(-2,4) not allowed
IF(1,1) allowed
IF(2,0) not allowed
IF(5,5) is allowed

Also ensure during array indexing, length of array doesnot exceed, otherwise it will reflects another type of array "array exceeds ....."

More detail read here

[Nour Sd]

Thank you for this explanation! It gave me a new idea :)