code: def get_correlation_matrix_from_columns(self):
          
          header_to_column = {}  # create index of headers
          for header in self.headers:
              header_to_column[header] = self.headers.index(header)
  
          data_to_test = []
          for header in self.headers_to_test:
              header_column = Matrix(self.data) \
                  .get_column(header_to_column[header])
  
              for i, value in enumerate(header_column):
                  header_column[i] = float(value)  # get float
  
              data_to_test.append(header_column)
  
          return self.get_correlation_matrix(data_to_test)
docs: Computes correlation matrix of columns
          :return: Correlation matrix of columns