index_subcase = findstrcmpDIS_nodes_num$SUBCASE;

This line of code finds the index of the string '$SUBCASE' in the cell array 'DIS_nodes_num' using the 'strcmp' function, which compares the string with each element of the cell array. The output of this function is a logical array where each element is true if the corresponding element in the cell array is equal to the string '$SUBCASE', and false otherwise. The 'find' function then returns the indices of the true elements in the logical array, which corresponds to the index of the string '$SUBCASE' in the cell array.