adaptive thresholding menas, the threshold value is not fixed, its depends on image or input data
In the first view, This code is messed. As you defined j=1:n, here j is scalar, also j(i,j)>> Here j >> representing vector. I didnot find any statement, which relate to calculate the threshold value or replacing vector elements based the threshold.
This statement finding the each element of 2D vector/matrix