Math

Understanding Matrix Determinant

The determinant has nothing to do with “equations”, it is a scalar.

The determinant is only applicable to square matrices, describing the volume of n n-dimensional vectors. For two dimensions, it is the area. A determinant of zero indicates that the matrix cannot span an n-dimensional space, at most n-1 dimensions, i.e., not full rank. So the volume is zero in n dimensions.

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Collisions in Poisson Process

This is problem that you may encounter, and I found a simple way to calculate it. The result looks correct after comparing with the actual data. A website receives an average of 1000 requests per hour, and can only handle one at a time, taking 1 second. When a request arrives, if the previous one has not been completed, an error will occur. How many errors will occur on average in an hour?

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Understanding Matrix Multiplication

Matrix multiplication has four cases, but essentially they are all vector operations.

  1. Vector dot product
  2. Matrix multiply vector (right multiply)
  3. Vector multiply matrix (left multiply)
  4. Matrix multiply matrix
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