Ukuran pemusatan

Pengantar Statistika di Python

Maggie Matsui

Content Developer, DataCamp

Data tidur mamalia

print(msleep)

                 name       genus   vore         order  ... sleep_cycle  awake  brainwt   bodywt
1             Cheetah    Acinonyx  carni     Carnivora  ...         NaN   11.9      NaN   50.000
2          Owl monkey       Aotus   omni      Primates  ...         NaN    7.0  0.01550    0.480
3     Mountain beaver  Aplodontia  herbi      Rodentia  ...         NaN    9.6      NaN    1.350
4 Greater short-ta...     Blarina   omni  Soricomorpha  ...    0.133333    9.1  0.00029    0.019
5                 Cow         Bos  herbi  Artiodactyla  ...    0.666667   20.0  0.42300  600.000
..                ...         ...    ...           ...  ...         ...    ...      ...      ...
79         Tree shrew      Tupaia   omni    Scandentia  ...    0.233333   15.1  0.00250    0.104
80 Bottle-nosed do...    Tursiops  carni       Cetacea  ...         NaN   18.8      NaN  173.330
81              Genet     Genetta  carni     Carnivora  ...         NaN   17.7  0.01750    2.000
82         Arctic fox      Vulpes  carni     Carnivora  ...         NaN   11.5  0.04450    3.380
83            Red fox      Vulpes  carni     Carnivora  ...    0.350000   14.2  0.05040    4.230

Histogram

Berapa lama mamalia di dataset ini biasanya tidur?

Berapa nilai tipikal?

Di mana pusat data?

Rata-rata
Median
Modus

Screen Shot 2020-07-02 at 11.01.16 AM.png

Ukuran pemusatan: rata-rata

                  name  sleep_total
1              Cheetah         12.1
2           Owl monkey         17.0
3      Mountain beaver         14.4
4   Greater short-t...         14.9
5                  Cow          4.0
..                 ...          ...

$\text{Waktu tidur rata-rata}=$

$$\frac{12.1 + 17.0 + 14.4 + 14.9 + ...}{83} = 10.43$$

import numpy as np
np.mean(msleep['sleep_total'])

10.43373

Ukuran pemusatan: median

msleep['sleep_total'].sort_values()

msleep['sleep_total'].sort_values().iloc[41]

10.1

np.median(msleep['sleep_total'])

10.1

Ukuran pemusatan: modus

Nilai yang paling sering muncul

msleep['sleep_total'].value_counts()

12.5    4
10.1    3
14.9    2
11.0    2
8.4     2
...
14.3    1
17.0    1
Name: sleep_total, Length: 65, dtype: int64

msleep['vore'].value_counts()

herbi      32
omni       20
carni      19
insecti     5
Name: vore, dtype: int64

import statistics
statistics.mode(msleep['vore'])

'herbi'

Menambahkan pencilan

# Subset msleep untuk memilih baris saat 'vore' sama dengan 'insecti'
msleep[msleep['vore'] == 'insecti']

                     name         genus     vore         order  sleep_total
22          Big brown bat     Eptesicus  insecti    Chiroptera         19.7
43       Little brown bat        Myotis  insecti    Chiroptera         19.9
62        Giant armadillo    Priodontes  insecti     Cingulata         18.1
67  Eastern american mole      Scalopus  insecti  Soricomorpha          8.4

Menambahkan pencilan

msleep[msleep['vore'] == "insecti"]['sleep_total'].agg([np.mean, np.median])

mean      16.53
median    18.9
Name: sleep_total, dtype: float64

Menambahkan pencilan

msleep[msleep['vore'] == 'insecti']

                     name         genus     vore         order  sleep_total
22          Big brown bat     Eptesicus  insecti    Chiroptera         19.7
43       Little brown bat        Myotis  insecti    Chiroptera         19.9
62        Giant armadillo    Priodontes  insecti     Cingulata         18.1
67  Eastern american mole      Scalopus  insecti  Soricomorpha          8.4

84    Mystery insectivore            ... insecti           ...          0.0

Menambahkan pencilan

msleep[msleep['vore'] == "insecti"]['sleep_total'].agg([np.mean, np.median])

mean      13.22
median    18.1
Name: sleep_total, dtype: float64

Rata-rata: 16.5 → 13.2

Median: 18.9 → 18.1

Ukuran mana yang dipakai?

# Impor matplotlib.pyplot sebagai plt
import matplotlib.pyplot as plt

# Histogram nilai
data['values'].hist()

# Tampilkan plot
plt.show()

histogram data simetris

Kemencengan (skew)

Condong kiri

Histogram data dengan sedikit nilai di kiri, meningkat ke lebih banyak nilai di kanan.

Condong kanan

Histogram data dengan banyak nilai di kiri, menurun ke sedikit nilai di kanan.

Ukuran mana yang dipakai?

Histogram data dengan sedikit nilai di kiri, meningkat ke lebih banyak nilai di kanan.

Histogram data dengan banyak nilai di kiri, menurun ke sedikit nilai di kanan.

Ayo berlatih!

Pengantar Statistika di Python