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Data Analysis and Importance of Groupby in Pandas but not Just pd.groupby

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Data Analysis and Importance of Groupby in Pandas but not Just pd.groupby

Originally published in dataqoil.com.
This blog will be continuously updated as I find new ways, tricks to make things work faster and easier.

Updates

What would you like to become in $y= mx+c$ ? Please don’t say +.

Introduction

I have been working with Pandas frequently and most of the time I have to do groupby. But I have noticed that pd.groupby is not always what I should do. Before diving into hands on experience, I would like to share some scenarios but first lets assume that you are working in a media company:

  1. What if your manager asks you to find the trend of content reach/growth in monthly basis so that they could know whether the contents have desired effect or not? Where you have one datetime column in timestamp format.
  2. What if your social media manager asks you to find the top 10 category of post with respect to profession of viewers so that they could make more focused and personalized contents dedicating to them and increase vies.
  3. You see there is a chance of being promoted and you want to give some valuable insights? What if you to present a best time to post a particular type of content. For example, a comedy or funny content might get best views during the day, a nature or motivating content might get good views during morning and a loving or musical content might get good views during the night.

Above 3 examples are some high level problem statement but in the ground level, almost every analyst have to group the data. Here in this blog, I am going to create a dummy data and perform some of analysis using groupby with it.

Creating a Dummy Data

The data will be generated randomly and thus it might not make any sense in the realworld but the goal of this blog is to explain/explore ways to do groupby in Pandas.

import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import numpy as np
import warnings

sns.set(rc={'figure.figsize':(40, 20),
                "axes.titlesize" : 24,
                "axes.labelsize" : 20,
                "xtick.labelsize" : 16,
                "ytick.labelsize" : 16})
plt.rc("figure", figsize=(16,8))
warnings.filterwarnings('ignore')
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Lets suppose your number of contents per day ranges from 3 to 7. Your views from the date of publish to 1 week could range from 2k to 100k and it also grows by 0.1% after reaching 100 views.

dates = pd.date_range(pd.to_datetime("2020-01-01"), pd.to_datetime("2021-01-01"))
times = ["Morning", "Day", "Night"]
categories = ["Motivating", "Musical", "Career", "News", "Funny"]
posts = list(range(5, 11))

content_dict = {"post_id":[], "date":[], "dtime": [], "category":[], "views": []}
post_id = 0

month = []
rate = 0.1

for d in dates:
    post_count = posts[np.random.randint(len(posts))]

    for p in range(post_count):
        if len(content_dict["date"])%100==0:
            rate+=0.1
        dtime = times[np.random.randint(len(times))]
        category = categories[np.random.randint(len(categories))]
        views = np.random.randint(20000, 100000) * rate

        content_dict["post_id"].append(post_id)
        content_dict["date"].append(d)
        content_dict["dtime"].append(dtime)
        content_dict["category"].append(category)
        content_dict["views"].append(views)
        post_id+=1

df = pd.DataFrame(content_dict, columns=list(content_dict.keys()))
df
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post_id date dtime category views
0 0 2020-01-01 Night Funny 19536.8
1 1 2020-01-01 Day Funny 5048.0
2 2 2020-01-01 Night News 13165.0
3 3 2020-01-01 Day Career 12326.8
4 4 2020-01-01 Morning News 19512.8
... ... ... ... ... ...
2735 2735 2021-01-01 Day Musical 180803.4
2736 2736 2021-01-01 Morning Motivating 203542.3
2737 2737 2021-01-01 Morning Musical 161295.1
2738 2738 2021-01-01 Morning Motivating 143900.9
2739 2739 2021-01-01 Night Career 84401.6

2740 rows × 5 columns

The data is ready and now we could start our analysis.

Number of Posts According to Category

Using normal groupby. More at here.

df.groupby("category").post_id.count().plot(kind="bar")


<AxesSubplot:xlabel='category'>
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png

Number of Views According to Category 

df.groupby("category").views.sum().plot(kind="bar")


<AxesSubplot:xlabel='category'>
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png

Pretty easy right?

Lets try something more.

Views and Count According to Day Time 

df.groupby("dtime").post_id.count().plot(kind="bar")


<AxesSubplot:xlabel='dtime'>
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png

df.groupby("dtime").views.sum().plot(kind="bar")


<AxesSubplot:xlabel='dtime'>
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png

Views According to Month

Using resample on date according to month. We could use week, quarter and also more flexible times to resample. (More at here)[https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.resample.html#pandas.DataFrame.resample].

df.resample(rule='M', on='date')["views"].sum().plot(kind="bar")


<AxesSubplot:xlabel='date'>
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png

In above step, we groupped the data according the month and took sum of views. But will it meet our next requirement?

Number of Views Per Month According to Category

Using Grouper to groupby month inside a groupby. More at here.

df.groupby(["category", pd.Grouper(key="date", freq="1M")]).views.sum().plot(kind="bar")


<AxesSubplot:xlabel='category,date'>
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png

Why not make our plot little bit more awesome?

vdf = df.groupby(["category", pd.Grouper(key="date", freq="1M")]).views.sum().rename("Views").reset_index()
vdf["date"] = vdf["date"].dt.date

def bar_plot(data, title="Views", xax=None,yax=None, hue=None):

    fig, ax = plt.subplots(figsize = (50, 30))   
    fig = sns.barplot(x = xax, y = yax, data = data, 
                 ci = None, ax=ax, hue=hue)
    plt.legend(fontsize=40)
    plt.yticks(fontsize=40)
    plt.xticks(fontsize=40, rotation=80)
    plt.title(title, fontsize=50)
    plt.xlabel(xax, fontsize=50)
    plt.ylabel(yax, fontsize=50)
    plt.show()
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I love to make my own custom visualization function. That gives me more flexibility and less time to tune sizes.

bar_plot(vdf, title="Views Plot", xax="date", yax="Views", hue="category")
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png

Can you find some insights or make some argument by looking over above data? Your result will definately be different than mine because of the random data used on above.

Rate of Views Change Per Month 

df.groupby([pd.Grouper(key="date", freq="1M")]).views.sum().pct_change().plot(kind="line")


<AxesSubplot:xlabel='date'>
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png

Rate of Views Change Per Month According to Category

Using shift inside the groupby object.

vdf = df.groupby(["category", pd.Grouper(key="date", freq="1M")]).views.sum().rename("Sums").reset_index()
lags = vdf.groupby("category").Sums.shift(1)
vdf["Rate"] = (vdf["Sums"]-lags)/lags
vdf
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category date Sums Rate
0 Career 2020-01-31 738533.2 NaN
1 Career 2020-02-29 1199889.7 0.624693
2 Career 2020-03-31 1913763.8 0.594950
3 Career 2020-04-30 3330908.0 0.740501
4 Career 2020-05-31 3390679.1 0.017944
... ... ... ... ...
58 News 2020-08-31 4054761.3 0.221326
59 News 2020-09-30 4865650.4 0.199984
60 News 2020-10-31 4976088.2 0.022697
61 News 2020-11-30 5903048.6 0.186283
62 News 2020-12-31 9044649.8 0.532200

63 rows × 4 columns

sns.lineplot(data=vdf,x="date", y="Rate", hue="category")


<AxesSubplot:xlabel='date', ylabel='Rate'>
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png

Because of being random data, we can not find any valuable information but we can see that the views has been decreased up to negative values in months like June. Lets verify that.

vdf[vdf.Rate<0]
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category date Sums Rate
5 Career 2020-06-30 3044816.8 -0.102004
11 Career 2020-12-31 8259240.0 -0.183001
12 Career 2021-01-31 84401.6 -0.989781
16 Funny 2020-04-30 2716427.3 -0.029595
21 Funny 2020-09-30 5526894.3 -0.108572
23 Funny 2020-11-30 5058885.1 -0.180990
30 Motivating 2020-06-30 3270395.5 -0.029415
33 Motivating 2020-09-30 4252837.6 -0.032287
36 Motivating 2020-12-31 6643837.5 -0.075897
37 Motivating 2021-01-31 347443.2 -0.947704
42 Musical 2020-05-31 2558136.9 -0.110001
47 Musical 2020-10-31 5345765.1 -0.058601
50 Musical 2021-01-31 621339.5 -0.933231
57 News 2020-07-31 3319967.6 -0.035456

More ways and ideas will be updated soon.

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