在 keras.argmax 中，ax =-1的含义是什么？

我是一个初学者在 Keras，需要帮助来理解 keras.argmax(a, axis=-1)和 keras.max(a, axis=-1)。当 a.shape = (19, 19, 5, 80)时，axis=-1的意义是什么？那么 keras.argmax(a, axis=-1)和 keras.max(a, axis=-1)的输出呢？

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This means that the index that will be returned by argmax will be taken from the last axis.

Your data has some shape (19,19,5,80). This means:

  • Axis 0 = 19 elements
  • Axis 1 = 19 elements
  • Axis 2 = 5 elements
  • Axis 3 = 80 elements

Now, negative numbers work exactly like in python lists, in numpy arrays, etc. Negative numbers represent the inverse order:

  • Axis -1 = 80 elements
  • Axis -2 = 5 elements
  • Axis -3 = 19 elements
  • Axis -4 = 19 elements

When you pass the axis parameter to the argmax function, the indices returned will be based on this axis. Your results will lose this specific axes, but keep the others.

See what shape argmax will return for each index:

  • K.argmax(a,axis= 0 or -4) returns (19,5,80) with values from 0 to 18
  • K.argmax(a,axis= 1 or -3) returns (19,5,80) with values from 0 to 18
  • K.argmax(a,axis= 2 or -2) returns (19,19,80) with values from 0 to 4
  • K.argmax(a,axis= 3 or -1) returns (19,19,5) with values from 0 to 79

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