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changes for Q29

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Charles
2020-05-28 15:35:39 -07:00
parent 493c48d101
commit 19af334130
6 changed files with 50 additions and 42 deletions
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37
100_Numpy_exercises_with_hints_with_solutions.md
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@@ -72,8 +72,8 @@ print(Z)
`hint: reshape`
```python
nz = np.nonzero([1,2,0,0,4,0])
print(nz)
Z = np.arange(9).reshape(3, 3)
print(Z)
```
#### 10. Find indices of non-zero elements from [1,2,0,0,4,0] (★☆☆)
`hint: np.nonzero`
@@ -264,13 +264,16 @@ print(np.array(0) // np.array(0))
print(np.array([np.nan]).astype(int).astype(float))
```
#### 29. How to round away from zero a float array ? (★☆☆)
`hint: np.uniform, np.copysign, np.ceil, np.abs`
`hint: np.uniform, np.copysign, np.ceil, np.abs, np.where`
```python
# Author: Charles R Harris
Z = np.random.uniform(-10,+10,10)
print (np.copysign(np.ceil(np.abs(Z)), Z))
print(np.copysign(np.ceil(np.abs(Z)), Z))
# More readable but less efficient
print(np.where(Z>0, np.ceil(Z), np.floor(Z)))
```
#### 30. How to find common values between two arrays? (★☆☆)
`hint: np.intersect1d`
@@ -292,8 +295,8 @@ Z = np.ones(1) / 0
_ = np.seterr(**defaults)
# Equivalently with a context manager
nz = np.nonzero([1,2,0,0,4,0])
print(nz)
with np.errstate(all="ignore"):
np.arange(3) / 0
```
#### 32. Is the following expressions true? (★☆☆)
```python
@@ -308,9 +311,9 @@ np.sqrt(-1) == np.emath.sqrt(-1)
`hint: np.datetime64, np.timedelta64`
```python
yesterday = np.datetime64('today', 'D') - np.timedelta64(1, 'D')
today = np.datetime64('today', 'D')
tomorrow = np.datetime64('today', 'D') + np.timedelta64(1, 'D')
yesterday = np.datetime64('today') - np.timedelta64(1)
today = np.datetime64('today')
tomorrow = np.datetime64('today') + np.timedelta64(1)
```
#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆)
`hint: np.arange(dtype=datetime64['D'])`
@@ -331,17 +334,17 @@ np.divide(A,2,out=A)
np.negative(A,out=A)
np.multiply(A,B,out=A)
```
#### 36. Extract the integer part of a random array using 5 different methods (★★☆)
`hint: %, np.floor, np.ceil, astype, np.trunc`
#### 36. Extract the integer part of a random array of positive numbers using 4 different methods (★★☆)
`hint: %, np.floor, astype, np.trunc`
```python
Z = np.random.uniform(0,10,10)
print (Z - Z%1)
print (np.floor(Z))
print (np.ceil(Z)-1)
print (Z.astype(int))
print (np.trunc(Z))
print(Z - Z%1)
print(Z // 1)
print(np.floor(Z))
print(Z.astype(int))
print(np.trunc(Z))
```
#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆)
`hint: np.arange`
@@ -717,7 +720,7 @@ print(pd.Series(D).groupby(S).mean())
A = np.random.uniform(0,1,(5,5))
B = np.random.uniform(0,1,(5,5))
# Slow version
# Slow version
np.diag(np.dot(A, B))
# Fast version