import pandas as pd
fish = pd.read_csv('https://bit.ly/fish_csv_data')
fish.head()
Species | Weight | Length | Diagonal | Height | Width | |
---|---|---|---|---|---|---|
0 | Bream | 242.0 | 25.4 | 30.0 | 11.5200 | 4.0200 |
1 | Bream | 290.0 | 26.3 | 31.2 | 12.4800 | 4.3056 |
2 | Bream | 340.0 | 26.5 | 31.1 | 12.3778 | 4.6961 |
3 | Bream | 363.0 | 29.0 | 33.5 | 12.7300 | 4.4555 |
4 | Bream | 430.0 | 29.0 | 34.0 | 12.4440 | 5.1340 |
print(pd.unique(fish['Species']))
['Bream' 'Roach' 'Whitefish' 'Parkki' 'Perch' 'Pike' 'Smelt']
fish_input = fish[['Weight','Length','Diagonal','Height','Width']].to_numpy()
print(fish_input[:5])
[[242. 25.4 30. 11.52 4.02 ] [290. 26.3 31.2 12.48 4.3056] [340. 26.5 31.1 12.3778 4.6961] [363. 29. 33.5 12.73 4.4555] [430. 29. 34. 12.444 5.134 ]]
fish_target = fish['Species'].to_numpy()
from sklearn.model_selection import train_test_split
train_input, test_input, train_target, test_target = train_test_split(
fish_input, fish_target, random_state=42)
from sklearn.preprocessing import StandardScaler
ss = StandardScaler()
ss.fit(train_input)
train_scaled = ss.transform(train_input)
test_scaled = ss.transform(test_input)
from sklearn.neighbors import KNeighborsClassifier
kn = KNeighborsClassifier(n_neighbors=3)
kn.fit(train_scaled, train_target)
print(kn.score(train_scaled, train_target))
print(kn.score(test_scaled, test_target))
0.8907563025210085 0.85
print(kn.classes_)
['Bream' 'Parkki' 'Perch' 'Pike' 'Roach' 'Smelt' 'Whitefish']
print(kn.predict(test_scaled[:5]))
['Perch' 'Smelt' 'Pike' 'Perch' 'Perch']
import numpy as np
proba = kn.predict_proba(test_scaled[:5])
print(np.round(proba, decimals=4))
[[0. 0. 1. 0. 0. 0. 0. ] [0. 0. 0. 0. 0. 1. 0. ] [0. 0. 0. 1. 0. 0. 0. ] [0. 0. 0.6667 0. 0.3333 0. 0. ] [0. 0. 0.6667 0. 0.3333 0. 0. ]]
distances, indexes = kn.kneighbors(test_scaled[3:4])
print(train_target[indexes])
[['Roach' 'Perch' 'Perch']]
import numpy as np
import matplotlib.pyplot as plt
z = np.arange(-5, 5, 0.1)
phi = 1 / (1 + np.exp(-z))
plt.plot(z, phi)
plt.xlabel('z')
plt.ylabel('phi')
plt.show()
char_arr = np.array(['A', 'B', 'C', 'D', 'E'])
print(char_arr[[True, False, True, False, False]])
['A' 'C']
bream_smelt_indexes = (train_target == 'Bream') | (train_target == 'Smelt')
train_bream_smelt = train_scaled[bream_smelt_indexes]
target_bream_smelt = train_target[bream_smelt_indexes]
from sklearn.linear_model import LogisticRegression
lr = LogisticRegression()
lr.fit(train_bream_smelt, target_bream_smelt)
LogisticRegression()In a Jupyter environment, please rerun this cell to show the HTML representation or trust the notebook.
LogisticRegression()
print(lr.predict(train_bream_smelt[:5]))
['Bream' 'Smelt' 'Bream' 'Bream' 'Bream']
print(lr.predict_proba(train_bream_smelt[:5]))
[[0.99759855 0.00240145] [0.02735183 0.97264817] [0.99486072 0.00513928] [0.98584202 0.01415798] [0.99767269 0.00232731]]
print(lr.classes_)
['Bream' 'Smelt']
print(lr.coef_, lr.intercept_)
[[-0.4037798 -0.57620209 -0.66280298 -1.01290277 -0.73168947]] [-2.16155132]
decisions = lr.decision_function(train_bream_smelt[:5])
print(decisions)
[-6.02927744 3.57123907 -5.26568906 -4.24321775 -6.0607117 ]
from scipy.special import expit
print(expit(decisions))
[0.00240145 0.97264817 0.00513928 0.01415798 0.00232731]
lr = LogisticRegression(C=20, max_iter=1000)
lr.fit(train_scaled, train_target)
print(lr.score(train_scaled, train_target))
print(lr.score(test_scaled, test_target))
0.9327731092436975 0.925
print(lr.predict(test_scaled[:5]))
['Perch' 'Smelt' 'Pike' 'Roach' 'Perch']
proba = lr.predict_proba(test_scaled[:5])
print(np.round(proba, decimals=3))
[[0. 0.014 0.841 0. 0.136 0.007 0.003] [0. 0.003 0.044 0. 0.007 0.946 0. ] [0. 0. 0.034 0.935 0.015 0.016 0. ] [0.011 0.034 0.306 0.007 0.567 0. 0.076] [0. 0. 0.904 0.002 0.089 0.002 0.001]]
print(lr.classes_)
['Bream' 'Parkki' 'Perch' 'Pike' 'Roach' 'Smelt' 'Whitefish']
print(lr.coef_.shape, lr.intercept_.shape)
(7, 5) (7,)
decision = lr.decision_function(test_scaled[:5])
print(np.round(decision, decimals=2))
[[ -6.5 1.03 5.16 -2.73 3.34 0.33 -0.63] [-10.86 1.93 4.77 -2.4 2.98 7.84 -4.26] [ -4.34 -6.23 3.17 6.49 2.36 2.42 -3.87] [ -0.68 0.45 2.65 -1.19 3.26 -5.75 1.26] [ -6.4 -1.99 5.82 -0.11 3.5 -0.11 -0.71]]
from scipy.special import softmax
proba = softmax(decision, axis=1)
print(np.round(proba, decimals=3))
[[0. 0.014 0.841 0. 0.136 0.007 0.003] [0. 0.003 0.044 0. 0.007 0.946 0. ] [0. 0. 0.034 0.935 0.015 0.016 0. ] [0.011 0.034 0.306 0.007 0.567 0. 0.076] [0. 0. 0.904 0.002 0.089 0.002 0.001]]