🤖 ML

Session 9 DF.Describe() function overview

📅 May 09, 2026

📓

Jupyter Notebook

In [1]:

import pandas as pd
from sklearn.datasets import load_iris

In [2]:

iris = load_iris()
table= pd.DataFrame(iris.data, columns = iris.feature_names)

In [3]:

iris

Out[3]:

{'data': array([[5.1, 3.5, 1.4, 0.2],
        [4.9, 3. , 1.4, 0.2],
        [4.7, 3.2, 1.3, 0.2],
        [4.6, 3.1, 1.5, 0.2],
        [5. , 3.6, 1.4, 0.2],
        [5.4, 3.9, 1.7, 0.4],
        [4.6, 3.4, 1.4, 0.3],
        [5. , 3.4, 1.5, 0.2],
        [4.4, 2.9, 1.4, 0.2],
        [4.9, 3.1, 1.5, 0.1],
        [5.4, 3.7, 1.5, 0.2],
        [4.8, 3.4, 1.6, 0.2],
        [4.8, 3. , 1.4, 0.1],
        [4.3, 3. , 1.1, 0.1],
        [5.8, 4. , 1.2, 0.2],
        [5.7, 4.4, 1.5, 0.4],
        [5.4, 3.9, 1.3, 0.4],
        [5.1, 3.5, 1.4, 0.3],
        [5.7, 3.8, 1.7, 0.3],
        [5.1, 3.8, 1.5, 0.3],
        [5.4, 3.4, 1.7, 0.2],
        [5.1, 3.7, 1.5, 0.4],
        [4.6, 3.6, 1. , 0.2],
        [5.1, 3.3, 1.7, 0.5],
        [4.8, 3.4, 1.9, 0.2],
        [5. , 3. , 1.6, 0.2],
        [5. , 3.4, 1.6, 0.4],
        [5.2, 3.5, 1.5, 0.2],
        [5.2, 3.4, 1.4, 0.2],
        [4.7, 3.2, 1.6, 0.2],
        [4.8, 3.1, 1.6, 0.2],
        [5.4, 3.4, 1.5, 0.4],
        [5.2, 4.1, 1.5, 0.1],
        [5.5, 4.2, 1.4, 0.2],
        [4.9, 3.1, 1.5, 0.2],
        [5. , 3.2, 1.2, 0.2],
        [5.5, 3.5, 1.3, 0.2],
        [4.9, 3.6, 1.4, 0.1],
        [4.4, 3. , 1.3, 0.2],
        [5.1, 3.4, 1.5, 0.2],
        [5. , 3.5, 1.3, 0.3],
        [4.5, 2.3, 1.3, 0.3],
        [4.4, 3.2, 1.3, 0.2],
        [5. , 3.5, 1.6, 0.6],
        [5.1, 3.8, 1.9, 0.4],
        [4.8, 3. , 1.4, 0.3],
        [5.1, 3.8, 1.6, 0.2],
        [4.6, 3.2, 1.4, 0.2],
        [5.3, 3.7, 1.5, 0.2],
        [5. , 3.3, 1.4, 0.2],
        [7. , 3.2, 4.7, 1.4],
        [6.4, 3.2, 4.5, 1.5],
        [6.9, 3.1, 4.9, 1.5],
        [5.5, 2.3, 4. , 1.3],
        [6.5, 2.8, 4.6, 1.5],
        [5.7, 2.8, 4.5, 1.3],
        [6.3, 3.3, 4.7, 1.6],
        [4.9, 2.4, 3.3, 1. ],
        [6.6, 2.9, 4.6, 1.3],
        [5.2, 2.7, 3.9, 1.4],
        [5. , 2. , 3.5, 1. ],
        [5.9, 3. , 4.2, 1.5],
        [6. , 2.2, 4. , 1. ],
        [6.1, 2.9, 4.7, 1.4],
        [5.6, 2.9, 3.6, 1.3],
        [6.7, 3.1, 4.4, 1.4],
        [5.6, 3. , 4.5, 1.5],
        [5.8, 2.7, 4.1, 1. ],
        [6.2, 2.2, 4.5, 1.5],
        [5.6, 2.5, 3.9, 1.1],
        [5.9, 3.2, 4.8, 1.8],
        [6.1, 2.8, 4. , 1.3],
        [6.3, 2.5, 4.9, 1.5],
        [6.1, 2.8, 4.7, 1.2],
        [6.4, 2.9, 4.3, 1.3],
        [6.6, 3. , 4.4, 1.4],
        [6.8, 2.8, 4.8, 1.4],
        [6.7, 3. , 5. , 1.7],
        [6. , 2.9, 4.5, 1.5],
        [5.7, 2.6, 3.5, 1. ],
        [5.5, 2.4, 3.8, 1.1],
        [5.5, 2.4, 3.7, 1. ],
        [5.8, 2.7, 3.9, 1.2],
        [6. , 2.7, 5.1, 1.6],
        [5.4, 3. , 4.5, 1.5],
        [6. , 3.4, 4.5, 1.6],
        [6.7, 3.1, 4.7, 1.5],
        [6.3, 2.3, 4.4, 1.3],
        [5.6, 3. , 4.1, 1.3],
        [5.5, 2.5, 4. , 1.3],
        [5.5, 2.6, 4.4, 1.2],
        [6.1, 3. , 4.6, 1.4],
        [5.8, 2.6, 4. , 1.2],
        [5. , 2.3, 3.3, 1. ],
        [5.6, 2.7, 4.2, 1.3],
        [5.7, 3. , 4.2, 1.2],
        [5.7, 2.9, 4.2, 1.3],
        [6.2, 2.9, 4.3, 1.3],
        [5.1, 2.5, 3. , 1.1],
        [5.7, 2.8, 4.1, 1.3],
        [6.3, 3.3, 6. , 2.5],
        [5.8, 2.7, 5.1, 1.9],
        [7.1, 3. , 5.9, 2.1],
        [6.3, 2.9, 5.6, 1.8],
        [6.5, 3. , 5.8, 2.2],
        [7.6, 3. , 6.6, 2.1],
        [4.9, 2.5, 4.5, 1.7],
        [7.3, 2.9, 6.3, 1.8],
        [6.7, 2.5, 5.8, 1.8],
        [7.2, 3.6, 6.1, 2.5],
        [6.5, 3.2, 5.1, 2. ],
        [6.4, 2.7, 5.3, 1.9],
        [6.8, 3. , 5.5, 2.1],
        [5.7, 2.5, 5. , 2. ],
        [5.8, 2.8, 5.1, 2.4],
        [6.4, 3.2, 5.3, 2.3],
        [6.5, 3. , 5.5, 1.8],
        [7.7, 3.8, 6.7, 2.2],
        [7.7, 2.6, 6.9, 2.3],
        [6. , 2.2, 5. , 1.5],
        [6.9, 3.2, 5.7, 2.3],
        [5.6, 2.8, 4.9, 2. ],
        [7.7, 2.8, 6.7, 2. ],
        [6.3, 2.7, 4.9, 1.8],
        [6.7, 3.3, 5.7, 2.1],
        [7.2, 3.2, 6. , 1.8],
        [6.2, 2.8, 4.8, 1.8],
        [6.1, 3. , 4.9, 1.8],
        [6.4, 2.8, 5.6, 2.1],
        [7.2, 3. , 5.8, 1.6],
        [7.4, 2.8, 6.1, 1.9],
        [7.9, 3.8, 6.4, 2. ],
        [6.4, 2.8, 5.6, 2.2],
        [6.3, 2.8, 5.1, 1.5],
        [6.1, 2.6, 5.6, 1.4],
        [7.7, 3. , 6.1, 2.3],
        [6.3, 3.4, 5.6, 2.4],
        [6.4, 3.1, 5.5, 1.8],
        [6. , 3. , 4.8, 1.8],
        [6.9, 3.1, 5.4, 2.1],
        [6.7, 3.1, 5.6, 2.4],
        [6.9, 3.1, 5.1, 2.3],
        [5.8, 2.7, 5.1, 1.9],
        [6.8, 3.2, 5.9, 2.3],
        [6.7, 3.3, 5.7, 2.5],
        [6.7, 3. , 5.2, 2.3],
        [6.3, 2.5, 5. , 1.9],
        [6.5, 3. , 5.2, 2. ],
        [6.2, 3.4, 5.4, 2.3],
        [5.9, 3. , 5.1, 1.8]]),
 'target': array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
        0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]),
 'frame': None,
 'target_names': array(['setosa', 'versicolor', 'virginica'], dtype='<U10'),
 'DESCR': '.. _iris_dataset:\n\nIris plants dataset\n--------------------\n\n**Data Set Characteristics:**\n\n:Number of Instances: 150 (50 in each of three classes)\n:Number of Attributes: 4 numeric, predictive attributes and the class\n:Attribute Information:\n    - sepal length in cm\n    - sepal width in cm\n    - petal length in cm\n    - petal width in cm\n    - class:\n            - Iris-Setosa\n            - Iris-Versicolour\n            - Iris-Virginica\n\n:Summary Statistics:\n\n============== ==== ==== ======= ===== ====================\n                Min  Max   Mean    SD   Class Correlation\n============== ==== ==== ======= ===== ====================\nsepal length:   4.3  7.9   5.84   0.83    0.7826\nsepal width:    2.0  4.4   3.05   0.43   -0.4194\npetal length:   1.0  6.9   3.76   1.76    0.9490  (high!)\npetal width:    0.1  2.5   1.20   0.76    0.9565  (high!)\n============== ==== ==== ======= ===== ====================\n\n:Missing Attribute Values: None\n:Class Distribution: 33.3% for each of 3 classes.\n:Creator: R.A. Fisher\n:Donor: Michael Marshall (MARSHALL%PLU@io.arc.nasa.gov)\n:Date: July, 1988\n\nThe famous Iris database, first used by Sir R.A. Fisher. The dataset is taken\nfrom Fisher\'s paper. Note that it\'s the same as in R, but not as in the UCI\nMachine Learning Repository, which has two wrong data points.\n\nThis is perhaps the best known database to be found in the\npattern recognition literature.  Fisher\'s paper is a classic in the field and\nis referenced frequently to this day.  (See Duda & Hart, for example.)  The\ndata set contains 3 classes of 50 instances each, where each class refers to a\ntype of iris plant.  One class is linearly separable from the other 2; the\nlatter are NOT linearly separable from each other.\n\n.. dropdown:: References\n\n  - Fisher, R.A. "The use of multiple measurements in taxonomic problems"\n    Annual Eugenics, 7, Part II, 179-188 (1936); also in "Contributions to\n    Mathematical Statistics" (John Wiley, NY, 1950).\n  - Duda, R.O., & Hart, P.E. (1973) Pattern Classification and Scene Analysis.\n    (Q327.D83) John Wiley & Sons.  ISBN 0-471-22361-1.  See page 218.\n  - Dasarathy, B.V. (1980) "Nosing Around the Neighborhood: A New System\n    Structure and Classification Rule for Recognition in Partially Exposed\n    Environments".  IEEE Transactions on Pattern Analysis and Machine\n    Intelligence, Vol. PAMI-2, No. 1, 67-71.\n  - Gates, G.W. (1972) "The Reduced Nearest Neighbor Rule".  IEEE Transactions\n    on Information Theory, May 1972, 431-433.\n  - See also: 1988 MLC Proceedings, 54-64.  Cheeseman et al"s AUTOCLASS II\n    conceptual clustering system finds 3 classes in the data.\n  - Many, many more ...\n',
 'feature_names': ['sepal length (cm)',
  'sepal width (cm)',
  'petal length (cm)',
  'petal width (cm)'],
 'filename': 'iris.csv',
 'data_module': 'sklearn.datasets.data'}

In [4]:

table

Out[4]:

	sepal length (cm)	sepal width (cm)	petal length (cm)	petal width (cm)
0	5.1	3.5	1.4	0.2
1	4.9	3.0	1.4	0.2
2	4.7	3.2	1.3	0.2
3	4.6	3.1	1.5	0.2
4	5.0	3.6	1.4	0.2
...	...	...	...	...
145	6.7	3.0	5.2	2.3
146	6.3	2.5	5.0	1.9
147	6.5	3.0	5.2	2.0
148	6.2	3.4	5.4	2.3
149	5.9	3.0	5.1	1.8

150 rows × 4 columns

In [5]:

# numerical variablek ko statical summary dinxa 
table.describe()

Out[5]:

	sepal length (cm)	sepal width (cm)	petal length (cm)	petal width (cm)
count	150.000000	150.000000	150.000000	150.000000
mean	5.843333	3.057333	3.758000	1.199333
std	0.828066	0.435866	1.765298	0.762238
min	4.300000	2.000000	1.000000	0.100000
25%	5.100000	2.800000	1.600000	0.300000
50%	5.800000	3.000000	4.350000	1.300000
75%	6.400000	3.300000	5.100000	1.800000
max	7.900000	4.400000	6.900000	2.500000

Pandas `df.describe()` Complete Notes¶

Introduction¶

df.describe() भनेको Pandas को एउटा method हो जसले dataset को statistical summary दिन्छ।

यो मुख्य रूपमा:

Exploratory Data Analysis (EDA)
Data Understanding
Data Cleaning अघि inspection
Machine Learning preprocessing

को लागि प्रयोग गरिन्छ।

Basic Syntax¶

df.describe()

Why We Use `df.describe()`¶

ठूलो dataset manually analyze गर्न गाह्रो हुन्छ।

त्यसैले describe() ले:

quick overview दिन्छ
numerical statistics देखाउँछ
missing values पत्ता लगाउन मद्दत गर्छ
outliers detect गर्न मद्दत गर्छ
data distribution बुझ्न सहयोग गर्छ

Example¶

import pandas as pd

data = {
    "Age": [20, 22, 25, 30, 35],
    "Salary": [20000, 25000, 30000, 40000, 50000]
}

df = pd.DataFrame(data)

print(df.describe())

Output Explanation¶

Statistic	Meaning
count	non-null values count
mean	average value
std	standard deviation
min	minimum value
25%	first quartile (Q1)
50%	median
75%	third quartile (Q3)
max	maximum value

Detailed Explanation¶

1. count¶

Meaning¶

non-null values कति छन्

Usecase¶

missing values detect गर्न

Example¶

df.describe()

यदि dataset मा 100 rows छन् तर count = 90 आयो भने:

10 missing values छन्

2. mean¶

Meaning¶

average value

Formula¶

Mean = Sum of all values / Total number of values

Usecase¶

average salary
average age
overall trend

Example¶

df["Salary"].mean()

3. std (Standard Deviation)¶

Meaning¶

data mean बाट कति spread भएको छ

Interpretation¶

std Value	Meaning
low std	data close together
high std	data highly spread

Usecase¶

variability measure
consistency check
outlier detection

Example¶

df["Salary"].std()

4. min¶

Meaning¶

सबैभन्दा सानो value

Usecase¶

lowest value पत्ता लगाउन

Example¶

df["Salary"].min()

5. 25% (Q1)¶

Meaning¶

25% data यो value भन्दा तल हुन्छ

Usecase¶

lower distribution बुझ्न

6. 50% (Median)¶

Meaning¶

middle value

Important¶

median outlier resistant हुन्छ

Usecase¶

skewed data analyze गर्न

7. 75% (Q3)¶

Meaning¶

75% data यो value भन्दा तल हुन्छ

Usecase¶

upper distribution बुझ्न

8. max¶

Meaning¶

सबैभन्दा ठूलो value

Usecase¶

highest value पत्ता लगाउन

Real World Usecases¶

1. Missing Value Detection¶

df.describe()

यदि count कम आयो भने:

missing values छन्

2. Outlier Detection¶

यदि:

max धेरै ठूलो
std धेरै high
mean unusual

भयो भने:

outlier हुन सक्छ

Example¶

mean	max
50	10000

→ suspicious value

3. Data Distribution Analysis¶

25%, 50%, 75% compare गरेर:

skewness
spread
balance

बुझ्न सकिन्छ

4. Machine Learning Preprocessing¶

ML अघि:

scaling चाहिन्छ?
normalization चाहिन्छ?
transformation चाहिन्छ?

भन्ने कुरा analyze गर्न मद्दत गर्छ।

Categorical Data Analysis¶

df.describe(include='object')

Output¶

Statistic	Meaning
count	non-null values
unique	unique categories
top	most frequent value
freq	frequency of top value

Example¶

df.describe(include='object')

Column	City
count	100
unique	5
top	Kathmandu
freq	40

Advanced Usage¶

1. Include All Columns¶

df.describe(include='all')

2. Custom Percentiles¶

df.describe(percentiles=[0.1, 0.5, 0.9])

Difference Between Mean and Median¶

Mean	Median
average value	middle value
affected by outliers	resistant to outliers
sensitive	robust

Typical Data Science Workflow¶

Step 1: Load Dataset¶

df = pd.read_csv("data.csv")

Step 2: Basic Information¶

df.info()

Step 3: Statistical Summary¶

df.describe()

Step 4: Missing Values¶

df.isnull().sum()

Step 5: Visualization¶

import seaborn as sns

sns.boxplot(data=df)

Advantages of `df.describe()`¶

Fast overview
Easy statistical understanding
Helps in EDA
Detects anomalies
Finds missing values
Useful before ML modeling

Limitations¶

By default numerical columns मात्र analyze गर्छ
full visualization दिदैन
correlation देखाउँदैन

Summary¶

df.describe() को main purpose भनेको dataset को quick statistical overview दिनु हो।

यसले:

average
spread
minimum
maximum
quartiles
missing values

जस्ता important insights दिन्छ।

Data Science, Data Analysis, Machine Learning मा यो धेरै important EDA tool हो।

In [6]:

import numpy as np

In [7]:

x = [10,20,30,30,45,50,55,60,70,80]

In [8]:

np.mean(x)

Out[8]:

np.float64(45.0)

In [9]:

np.median(x)

Out[9]:

np.float64(47.5)

In [10]:

np.percentile(x, [25,50,75,100])

Out[10]:

array([30.  , 47.5 , 58.75, 80.  ])

In [11]:

np.std(x)

Out[11]:

np.float64(21.213203435596427)

In [12]:

np.var(x)

Out[12]:

np.float64(450.0)

← Back to ML

	sepal length (cm)	sepal width (cm)	petal length (cm)	petal width (cm)
0	5.1	3.5	1.4	0.2
1	4.9	3.0	1.4	0.2
2	4.7	3.2	1.3	0.2
3	4.6	3.1	1.5	0.2
4	5.0	3.6	1.4	0.2
...	...	...	...	...
145	6.7	3.0	5.2	2.3
146	6.3	2.5	5.0	1.9
147	6.5	3.0	5.2	2.0
148	6.2	3.4	5.4	2.3
149	5.9	3.0	5.1	1.8

	sepal length (cm)	sepal width (cm)	petal length (cm)	petal width (cm)
0	5.1	3.5	1.4	0.2
1	4.9	3.0	1.4	0.2
2	4.7	3.2	1.3	0.2
3	4.6	3.1	1.5	0.2
4	5.0	3.6	1.4	0.2
...	...	...	...	...
145	6.7	3.0	5.2	2.3
146	6.3	2.5	5.0	1.9
147	6.5	3.0	5.2	2.0
148	6.2	3.4	5.4	2.3
149	5.9	3.0	5.1	1.8

Session 9 DF.Describe() function overview

Jupyter Notebook

Pandas df.describe() Complete Notes¶

Introduction¶

Basic Syntax¶

Why We Use df.describe()¶

Example¶

Output Explanation¶

Detailed Explanation¶

1. count¶

Meaning¶

Usecase¶

Example¶

2. mean¶

Meaning¶

Formula¶

Usecase¶

Example¶

3. std (Standard Deviation)¶

Meaning¶

Interpretation¶

Usecase¶

Example¶

4. min¶

Meaning¶

Usecase¶

Example¶

5. 25% (Q1)¶

Meaning¶

Usecase¶

6. 50% (Median)¶

Meaning¶

Important¶

Usecase¶

7. 75% (Q3)¶

Meaning¶

Usecase¶

8. max¶

Meaning¶

Usecase¶

Real World Usecases¶

1. Missing Value Detection¶

2. Outlier Detection¶

Example¶

3. Data Distribution Analysis¶

4. Machine Learning Preprocessing¶

Categorical Data Analysis¶

Output¶

Example¶

Advanced Usage¶

1. Include All Columns¶

2. Custom Percentiles¶

Difference Between Mean and Median¶

Typical Data Science Workflow¶

Step 1: Load Dataset¶

Step 2: Basic Information¶

Step 3: Statistical Summary¶

Step 4: Missing Values¶

Step 5: Visualization¶

Advantages of df.describe()¶

Limitations¶

Summary¶

Pandas `df.describe()` Complete Notes¶

Why We Use `df.describe()`¶

Advantages of `df.describe()`¶

	sepal length (cm)	sepal width (cm)	petal length (cm)	petal width (cm)
0	5.1	3.5	1.4	0.2
1	4.9	3.0	1.4	0.2
2	4.7	3.2	1.3	0.2
3	4.6	3.1	1.5	0.2
4	5.0	3.6	1.4	0.2
...	...	...	...	...
145	6.7	3.0	5.2	2.3
146	6.3	2.5	5.0	1.9
147	6.5	3.0	5.2	2.0
148	6.2	3.4	5.4	2.3
149	5.9	3.0	5.1	1.8