I am just getting started using Mathematica. I have a code I developed in Matlab, but I realize now that Matlab does not calculate Macdonald functions of imaginary order. So, here I am with Mathematica. I have a *.csv file with numeric data array. I figured out how to read in array, but cannot find anything to instruct me how to extract element-wise values that I can use in computations. The convention of "{{ }}", or "[{ }]", or "[[ ]]" is not explained in any of the documentation, and no combination I try works. I am trying to extract, for instance, element at position [2,3] of the array to perform a calculation. The output I get is taking the entire array and performing the calculation on all elements. How do I get the calculation on the single element I want?

Dwight