def update_matrix(self, pair, input):

    self.matrix[pair][input]['n_obs'] = self.matrix[pair][input]['n_obs'] + 1

    n_total = 0
    for i in self.matrix[pair]:
        n_total += self.matrix[pair][i]['n_obs']

    for i in self.matrix[pair]:
        self.matrix[pair][i]['prob'] = self.matrix[pair][i]['n_obs'] / n_total