numpy

Question 1

create an array [a,…, n] with step size x

Answer 1

numpy.arange(a, n+1, x)

Question 2

add arr2 to the end of arr1

Answer 2

numpy.append(arr1, arr2)

Question 3

calculate std for arr

Answer 3

np.std(arr, ddof = 1)

Question 4

calculate the covariance of two arrs

Answer 4

np.cov(x,y)[0,1]

Question 5

calculate the correlation coefficient of two arrs

Answer 5

np.corrcoef(x, y)[0,1]

Question 6

the product of all elements in an array x

Answer 6

np.prod(x)

Question 7

create a new array and its elements are element wise sums from arr1 and arr2.

Answer 7

x = arr1 + arr2

Question 8

get an array of k zeros in it

Answer 8

numpy.zeros(k)

Question 9

mean of arr

Answer 9

arr.mean() or numpy.mean(arr)

Question 10

median of arr

Answer 10

np.median(arr)

Question 11

variance of an array

Answer 11

np.var(arr, ddof =1)

Question 12

the covariance of the two arrays

Answer 12

np.cov(arr1, arr2)[0,1]

Question 13

the covariance matrix of the two arrays

Answer 13

np.cov(arr1, arr2)

Question 14

correlation coefficient matrix of two arrays

Answer 14

np.corrcoef(arr1,arr2)

Question 15

log transform a column

Answer 15

df[‘log_value’] = np.log(df[‘value’])