Table 6 Algorithm of Calculating Frequency of Co-occurrent DescriptorName Pairs

k = max_line_number

DO while k ≥ 1

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   FOR DescriptorName_Pair(1)//The 1st pairs in CHD_RA

      COUNT its Frequency

   EndFor

   OUTPUT DescriptorName Pairs, Frequency INTO table

         CHD_RA_Frqncy

   DELETE all DescriptorName_Pair(1) from table

         CHD_RA

   k = max_line_number

ENDDO