code: def correlations(self):
          
          corr_df = self._sensors_num_df.corr()
          corr_names = []
          corrs = []
  
          for i in range(len(corr_df.index)):
              for j in range(len(corr_df.index)):
                  c_name = corr_df.index[i]
                  r_name = corr_df.columns[j]
                  corr_names.append("%s-%s" % (c_name, r_name))
                  corrs.append(corr_df.ix[i, j])
  
          corrs_all = pd.DataFrame(index=corr_names)
          corrs_all["value"] = corrs
          corrs_all = corrs_all.dropna().drop(
              corrs_all[(corrs_all["value"] == float(1))].index
          )
          corrs_all = corrs_all.drop(corrs_all[corrs_all["value"] == float(-1)].index)
  
          corrs_all = corrs_all.sort_values("value", ascending=False)
          corrs_all = corrs_all.drop_duplicates()
          return corrs_all
docs: Calculate the correlation coefficients.