In many cases, two co-occurring words have nearly the same frequency. In many other cases (like DET NN), the frequencies differ very much. The following plot shows the frequency classes of co-occurring words. Frequency classes are defined as the logarithm (with base 2) of the frequency rank. The size of the dots corresponds to the number of co-occurrences with the corresponding pair of frequency classes.
Note that the plot is usually not symmetric wrt. the main diagonal.
select round(log(w1_id-100)/log(2)) as fc1,round(log(w2_id-100)/log(2)) as fc2, round(log(count(*)))*.3 as rad from co_n where w1_id>100 and w2_id>100 group by fc1,fc2
5.2.10 Number of Sentence co-occurrences depending on frequency classes