text: column name to create two matrices. One matrix was created for the climate change discourse, and we 
  ﬁlled the cell whose column name and row name were among the top 50 list in the climate change 
  discourse with the frequency at which the two hashtags were associated in this discourse, and the 
  other cells were ﬁlled with 0. This was repeated for the global warming matrix. We thus obtained 
  two matrices with the same row and column names but diﬀerent values in the cells. Then, the two 
  matrices were input to the quadratic assignment procedure (QAP) [85] analysis provided by UCINET 
  software [86] to assess their correlation for each year. 
  
  **4. Results**
  
  4.1. General Descriptions 