100 narray exercises

This is narray version of 100 numpy exercises (Repository)

1. Import the numpy package under the name np (★☆☆)

   Python:

   import numpy as np

   Ruby:

   require "numo/narray"

2. Print the numpy version and the configuration (★☆☆)

   Python:

   print(np.__version__)
   np.show_config()

   Ruby:

3. Create a null vector of size 10 (★☆☆)

   Python:

   Z = np.zeros(10)
   print(Z)

   Ruby:

   p Numo::Int32.zeros(10)
   p Numo::Float64.zeros(10)
   p Numo::NArray[*[0]*10]

4. How to get the documentation of the numpy add function from the command line ? (★☆☆)

   Python:

   python -c "import numpy; numpy.info(numpy.add)"

   Ruby:

   ri 'Numo::DFloat#+'

5. Create a null vector of size 10 but the fifth value which is 1 (★☆☆)

   Python:

   Z = np.zeros(10)
   Z[4] = 1
   print(Z)

   Ruby:

   z = Numo::Float64.zeros(10)
   z[4] = 1
   p z

6. Create a vector with values ranging from 10 to 49 (★☆☆)

   Python:

   Z = np.arange(10,50)
   print(Z)

   Ruby:

   p Numo::Int32[10...50]
   p Numo::Int32[10..49]
   p Numo::Int32.new(40).seq(10)

7. Reverse a vector (first element becomes last) (★☆☆)

   Python:

   Z = np.arange(50)
   Z = Z[::-1]

   Ruby:

   Numo::Int32.new(50).seq.reverse

8. Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆)

   Python:

   Z = np.arange(9).reshape(3,3)
   print(Z)

   Ruby:

   Numo::Int32.new(3,3).seq

9. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)

   Python:

   nz = np.nonzero([1,2,0,0,4,0])
   print(nz)

   Ruby:

   p Numo::NArray[1,2,0,0,4,0].ne(0).where

10. Create a 3x3 identity matrix (★☆☆)

    Python:

    Z = np.eye(3)
    print(Z)

    Ruby:

    p Numo::Float64.eye(3)

11. Create a 3x3x3 array with random values (★☆☆)

    Python:

    Z = np.random.random((3,3,3))
    print(Z)

    Ruby:

    p Numo::Float64.new(3,3,3).rand

12. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆)

    Python:

    Z = np.random.random((10,10))
    Zmin, Zmax = Z.min(), Z.max()
    print(Zmin, Zmax)

    Ruby:

    p Numo::Float64.new(3,3,3).rand.minmax

13. Create a random vector of size 30 and find the mean value (★☆☆)

    Python:

    Z = np.random.random(30)
    m = Z.mean()
    print(m)

    Ruby:

    p Numo::Float64.new(30).rand.mean

14. Create a 2d array with 1 on the border and 0 inside (★☆☆)

    Python:

    Z = np.ones((10,10))
    Z[1:-1,1:-1] = 0

    Ruby:

    z = Numo::Float64.ones(10,10)
    z[1..-2,1..-2] = 0
    p z

15. What is the result of the following expression ? (★☆☆)

    Python:

    0 * np.nan
    np.nan == np.nan
    np.inf > np.nan
    np.nan - np.nan
    0.3 == 3 * 0.1

    Ruby:

    0 * Float::NAN
    Float::NAN == Float::NAN
    Float::INFINITY > Float::NAN
    Float::NAN - Float::NAN
    0.3 == 3 * 0.1

16. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆)

    Python:

    Z = np.diag(1+np.arange(4),k=-1)
    print(Z)

    Ruby:

    z = Numo::Int32.zeros(5,5)
    z.diagonal(-1)[] = Numo::Int32[1..4]
    p z

17. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆)

    Python:

    Z = np.zeros((8,8),dtype=int)
    Z[1::2,::2] = 1
    Z[::2,1::2] = 1
    print(Z)

    Ruby:

    x = Numo::Int32.new(1,8).seq
    y = Numo::Int32.new(8,1).seq
    z = (x+y)%2
    p z

18. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element ?

    Python:

    print(np.unravel_index(100,(6,7,8)))

    Ruby:

    # NArray allows unraveled index access
    z = Numo::Int32.new(6,7,8).seq
    p z[100]

19. Create a checkerboard 8x8 matrix using the tile function (★☆☆)

    Python:

    Z = np.tile( np.array([[0,1],[1,0]]), (4,4))
    print(Z)

    Ruby:

    TBD

20. Normalize a 5x5 random matrix (★☆☆)

    Python:

    Z = np.random.random((5,5))
    Zmax, Zmin = Z.max(), Z.min()
    Z = (Z - Zmin)/(Zmax - Zmin)
    print(Z)

    Ruby:

    z = Numo::Float64.new(5,5).rand
    zmin,zmax = z.minmax
    z = (z - zmin)/(zmax - zmin)
    p z

21. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆)

    Python:

    Z = np.dot(np.ones((5,3)), np.ones((3,2)))
    print(Z)

    Ruby:

    x = Numo::DFloat.ones(5,3)
    y = Numo::DFloat.ones(3,2)
    z = x.dot y
    p z

22. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆)

    Python:

    # Author: Evgeni Burovski
    
    Z = np.arange(11)
    Z[(3 < Z) & (Z <= 8)] *= -1

    Ruby:

    z = Numo::Int32.new(11).seq
    z[(3<z).and(z<=8)] *= -1

23. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)

    Python:

    Z = np.zeros((5,5))
    Z += np.arange(5)
    print(Z)

    Ruby:

    z = Numo::Float64.zeros(5,5)
    z += Numo::Int32.new(5).seq
    p z