# Getting started
# Numpy arrays are a great alternative to python lists
# Some of the key advantages of Numpy arrays are that they are fast, easy to work with,
# and give users the opportunity to perform calculations across entire arrays.

# In the following example, you will first create two Python lists. Then, you will import
# the numpy package and create numpy arrays out of the newly created lists.
# Ex:-----
# Create 2 new lists height and weight
height = [1.87,  1.87, 1.82, 1.91, 1.90, 1.85]
weight = [81.65, 97.52, 95.25, 92.98, 86.18, 88.45]

# Import the numpy package as np
import numpy as np

# Create 2 numpy arrays from height and weight
np_height = np.array(height)
np_weight = np.array(weight)

#print out type of np_height
print(type(np_height))
# -----

# Element-wise calculations
# Now we can perform element-wise calculations on height and weight.
# For example, you could take all 6 of the height and weight observations above,
# and calculate the BMI for each observation with a single equation.
# These operations are very fast and computationally efficient.
# They are particularly helpful when you have 1000s of observations in your data.
# Ex: -----
# Calculate bmi
bmi = np_weight / np_height ** 2

# Print the result
print(bmi)
# -----

# Subsetting
# Another great feature of Numpy arrays is the ability to subset.
# For instance, if you wanted to know which observations in our BMI array are above 23,
# we could quickly subset it to find out.
# Ex: -----
# For a boolean response
bmi > 23

# Print only those observations above 23
bmi[bmi > 23]
# -----

# EXERCISE
# First, convert the list of weights from a list to a Numpy array.
# Then, convert all of the weights from kilograms to pounds.
# Use the scalar conversion of 2.2 lbs per kilogram to make your conversion.
# Lastly, print the resulting array of weights in pounds.
weight_kg = [81.65, 97.52, 95.25, 92.98, 86.18, 88.45]

import numpy as np

# Create a numpy array np_weight_kg from weight_kg
np_weight_kg = np.array(weight_kg)

# Create np_weight_lbs from np_weight_kg
np_weight_lbs = np_weight_kg * 2.2

# Print out np_weight_lbs
print(np_weight_lbs)