Error in array bounds

[Briette Esposito]

How do I resolve this error

Answer 1

[Arjun]

Hi @Briette Esposito,

The line "row = row + 1" is incorrectly placed inside the "for" loop, which causes row to increment with every trial, not after each row is processed. This leads to an index out-of-bounds error when "row" exceeds the number of rows in "blankarray".

This example clearly illustrates the cause of the problem:

Initial Setup:

• row = 1
• trials(1) = 5
• So the for loop will run: for a = 1 to 5

Inner For Loop:

• When a = 1, row = 1. Accessing blankarray(1,cloumn) is permitted
• When a = 2, row = 2. Accessing blankarray(2,column) is permitted
• When a = 3, row = 3. Accessing blankarray(3,cloumn) is permitted
• When a = 4, row = 4. Accessing blankarray(4,column) is permitted
• When a = 5, row = 5. Accessing blankarray(5,column) is not allowed because you are trying to access 5th row which does not exist since blankarray had only 4 rows in it hence the error "Index in position 1 exceeds array bounds. Index must not exceed 4".

This error can be resolved by carefully placing the update rule "row = row + 1" ensuring that the value of "row" does not exceed the number of rows in "blankarray" when trying to access "blankarray".

One such implementation is enclosed in the following code section:

blankarray = zeros(4,6);
row = 1;
while row < 5
    for a = 1:trials(row)
        if x(y,a) == 1
            blankarray(row,1) = blankarray(row,1) + 1;
        elseif x(y,a) == 2
            blankarray(row,2) = blankarray(row,2) + 1;
        elseif x(y,a) == 3
            blankarray(row,3) = blankarray(row,3) + 1;
        elseif x(y,a) == 4
            blankarray(row,4) = blankarray(row,4) + 1;
        elseif x(y,a) == 5
            blankarray(row,5) = blankarray(row,5) + 1;
        else x(y,a) == 6;
        end
    end
    row = row + 1; % Updating row at end of for loop.
end

I hope this helps!