numpy : argmin in multidimensional arrays

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  • TG
    #1

    numpy : argmin in multidimensional arrays

    Hi there.

    I am working with multi-dimensional arrays and I need to get
    coordinates of the min value in it.

    using myarray.argmin( ) returns the index in the flatten array, which is
    a first step, but I wonder if it is possible to get the coordinates
    directly as an array, rather than calculating them myself by using this
    flat index and the shape of the array.

    well, in fact i'm not sure to understand how argmin(myarray) works,
    when myarray is multidimensiona l.

    Thanks

    Tags: numpy argmin
    • Travis E. Oliphant
      #2
      Re: numpy : argmin in multidimensiona l arrays

      TG wrote:
      Hi there.
      >
      I am working with multi-dimensional arrays and I need to get
      coordinates of the min value in it.
      >
      using myarray.argmin( ) returns the index in the flatten array, which is
      a first step, but I wonder if it is possible to get the coordinates
      directly as an array, rather than calculating them myself by using this
      flat index and the shape of the array.
      >
      well, in fact i'm not sure to understand how argmin(myarray) works,
      when myarray is multidimensiona l.

      By default, the argmin method flattens the array and returns the flat
      index. You can get the corresponding element using

      myarray.flat[index]

      Alternatively, you can use the function unravel_index

      unravel_index(f lat_index, myarray.shape)

      to return an N-dimensional index.


      If you give an axis argument, then the minimum is found along the
      specified dimension and you get an N-1 dimensional array of indices that
      will all be between 1 and myarray.shape[axis]


      -Travis





        Comment

        • TG
          #3
          Re: numpy : argmin in multidimensiona l arrays

          thanks. unravel_index do the trick.

          Travis E. Oliphant wrote:
          TG wrote:
          Hi there.

          I am working with multi-dimensional arrays and I need to get
          coordinates of the min value in it.

          using myarray.argmin( ) returns the index in the flatten array, which is
          a first step, but I wonder if it is possible to get the coordinates
          directly as an array, rather than calculating them myself by using this
          flat index and the shape of the array.

          well, in fact i'm not sure to understand how argmin(myarray) works,
          when myarray is multidimensiona l.
          >
          >
          By default, the argmin method flattens the array and returns the flat
          index. You can get the corresponding element using
          >
          myarray.flat[index]
          >
          Alternatively, you can use the function unravel_index
          >
          unravel_index(f lat_index, myarray.shape)
          >
          to return an N-dimensional index.
          >
          >
          If you give an axis argument, then the minimum is found along the
          specified dimension and you get an N-1 dimensional array of indices that
          will all be between 1 and myarray.shape[axis]
          >
          >
          -Travis

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