Roll rows of a matrix independently

by

Sure you can do it using advanced indexing, whether it is the fastest way probably depends on your array size (if your rows are large it may not be):

rows, column_indices = np.ogrid[:A.shape[0], :A.shape[1]]

# Use always a negative shift, so that column_indices are valid.
# (could also use module operation)
r[r < 0] += A.shape[1]
column_indices = column_indices - r[:, np.newaxis]

result = A[rows, column_indices]

More Related Contents:

  1. numpy: most efficient frequency counts for unique values in an array
  2. Why is numpy’s einsum faster than numpy’s built in functions?
  3. Numpy sum elements in array based on its value
  4. Efficiently return the index of the first value satisfying condition in array
  5. Link ATLAS/MKL to an installed Numpy
  6. Bin elements per row – Vectorized 2D Bincount for NumPy
  7. Fastest way to grow a numpy numeric array
  8. Vectorized searchsorted numpy
  9. Implement MATLAB’s im2col ‘sliding’ in Python
  10. Python’s sum vs. NumPy’s numpy.sum
  11. Numpy: Fix array with rows of different lengths by filling the empty elements with zeros
  12. Why “numpy.any” has no short-circuit mechanism?
  13. Vectorizing Haversine distance calculation in Python
  14. Numpy and line intersections
  15. Why is numpy.array so slow?
  16. Efficient evaluation of a function at every cell of a NumPy array
  17. why isn’t numpy.mean multithreaded?
  18. Why list comprehension is much faster than numpy for multiplying arrays?
  19. Why is `np.sum(range(N))` very slow?
  20. Why is a `for` over a Python list faster than over a Numpy array?
  21. Performance: Matlab vs Python
  22. Are NumPy’s math functions faster than Python’s?
  23. Max in a sliding window in NumPy array
  24. Efficiently replace elements in array based on dictionary – NumPy / Python
  25. Why is Numpy much faster at creating a Zero array compared to replacing the values of an existing array with zeros?
  26. Getting days since last occurence in Pandas DataFrame?
  27. Multiple matrix multiplication
  28. Creating a numpy array of 3D coordinates from three 1D arrays
  29. Split Python sequence (time series/array) into subsequences with overlap
  30. numpy faster than numba and cython , how to improve numba code

Leave a Comment