how is axis indexed in numpy’s array?

by

By definition, the axis number of the dimension is the index of that dimension within the array’s shape. It is also the position used to access that dimension during indexing.

For example, if a 2D array a has shape (5,6), then you can access a[0,0] up to a[4,5]. Axis 0 is thus the first dimension (the “rows”), and axis 1 is the second dimension (the “columns”). In higher dimensions, where “row” and “column” stop really making sense, try to think of the axes in terms of the shapes and indices involved.

If you do .sum(axis=n), for example, then dimension n is collapsed and deleted, with each value in the new matrix equal to the sum of the corresponding collapsed values. For example, if b has shape (5,6,7,8), and you do c = b.sum(axis=2), then axis 2 (dimension with size 7) is collapsed, and the result has shape (5,6,8). Furthermore, c[x,y,z] is equal to the sum of all elements b[x,y,:,z].

More Related Contents:

  1. Is there a NumPy function to return the first index of something in an array?
  2. Understanding NumPy’s einsum
  3. Saving a Numpy array as an image
  4. How to one-hot-encode from a pandas column containing a list?
  5. Removing nan values from an array
  6. Why is numpy’s einsum faster than numpy’s built in functions?
  7. Using a pre-trained word embedding (word2vec or Glove) in TensorFlow
  8. Numpy index slice without losing dimension information
  9. Numpy: Get random set of rows from 2D array
  10. Select multiple ranges of columns in Pandas DataFrame
  11. How can I release memory after creating matplotlib figures
  12. Faster way of polygon intersection with shapely
  13. Find elements of array one nearest to elements of array two
  14. How to copy data from a numpy array to another
  15. How to convert list of numpy arrays into single numpy array?
  16. how to perform max/mean pooling on a 2d array using numpy
  17. find and delete from more-dimensional numpy array
  18. Initialise numpy array of unknown length
  19. Saving Matplotlib graphs to image as full screen
  20. Read a base 64 encoded image from memory using OpenCv python library
  21. Create new column based on values from other columns / apply a function of multiple columns, row-wise in Pandas
  22. Filtering (reducing) a NumPy Array
  23. How to replicate array to specific length array
  24. Cannot get minor grid lines to appear in matplotlib figure
  25. ImportError: No module named numpy on spark workers
  26. Automatic White Balancing with Grayworld assumption
  27. C++ conversion from NumPy array to Mat (OpenCV)
  28. How to use sklearn fit_transform with pandas and return dataframe instead of numpy array?
  29. numpy array TypeError: only integer scalar arrays can be converted to a scalar index
  30. Efficient dot products of large memory-mapped arrays

Leave a Comment