code: def _diff_matrix(x, lag):
      # compute the lag for a matrix (not a vector)
      m, _ = x.shape
      lag = min(
          m, lag
      )  # if lag > n, then we just want an empty array back
      return x[lag:m, :] - x[: m - lag, :]
  
file_path: pmdarima/pmdarima/utils/array.py
imports: from sklearn.utils import validation
  import numpy
  import pandas
  from ..compat import DTYPE
  from ._array import C_intgrt_vec
label_desc: Use image node_id 6 for calling a global function with example usage: _diff_matrix(x, lag) and returns: unknown