# NumPy Vector

## Get the vector norm

```
import numpy as np
from numpy import linalg as LA
v = np.array([3, 4])
n = LA.norm(v)
print(n) # 5.0
print(type(n)) # <class 'numpy.float64'>
```

linalg.norm returns the norm of NumPy array (vector) in numpy.float64, which is not float.

## Calculate the inner product of vectors

```
import numpy as np
v = np.array([1, 2])
w = np.array([3, 4])
i = np.dot(v, w)
print(i) # 11
print(type(i)) # <class 'numpy.int64'>
```

## Calculate the outer product of vectors

```
import numpy
a = numpy.array([1, 2])
b = numpy.array([3, 4])
c = numpy.outer(a, b)
print(c)
# [[3 4]
# [6 8]]
print(type(c)) # <class 'numpy.ndarray'>
```

## Calculate the angle between two vectors

```
import numpy as np
import numpy.linalg as LA
a = np.array([1, 2])
b = np.array([-5, 4])
inner = np.inner(a, b)
norms = LA.norm(a) * LA.norm(b)
cos = inner / norms
rad = np.arccos(np.clip(cos, -1.0, 1.0))
deg = np.rad2deg(rad)
print(rad) # 1.35970299357215
print(deg) # 77.9052429229879
```

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