visualize data in bar chart using python

Question

This is my data inside my PostgreSQL. I need to create a bar chart (y-axis: number of post, x-axis: student_id). so I run SQL Script in Python and visualise using python.

here is my code:

import psycopg2
import pandas as pd
import matplotlib.pyplot as plt

con = psycopg2.connect(
            host = "",
            database="",
            port="",
            user = "",
            password = "")

cur = con.cursor()

query= 'select student_id, count(student_id) as numberpost from forum group by student_id'

df=pd.read_sql(query,con)

plt.bar(x=df['student_id'],
        height=df['numberpost'])
plt.xticks(rotation = 45)
plt.show()

However, I didn't get the output as I want. This is the output that I get.

It should be student_id data in the x-axis, and numberpost data in the y-axis.

Anyone can help me how to solve this problem?

The problem seems to be the large range of student_id values, as it's read as integers. Maybe try passing them as strings instead? So plt.bar(x=df['student_id'].to_string(), ... — Energya
– Energya, Commented Oct 15, 2020 at 22:58
@Energya, I did that, but the output I got as below: <img src="drive.google.com/file/d/1yYFqoUUehj2aqTJZKvEt-g2qmQ6-heTG/…"> — atiqah yusri
– atiqah yusri, Commented Oct 17, 2020 at 18:13
Then you need to adjust your xticks accordingly, try searching for that — Energya
– Energya, Commented Oct 17, 2020 at 18:23

Energya · Accepted Answer · 2020-10-17 18:27:58Z

1

The problem seems to be the large range of student_id values, as it's read as integers.

Maybe try passing them as strings instead? So try

plt.bar(x=df['student_id'].to_string(), ...

answered Oct 17, 2020 at 18:27

Energya

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Comments

Ray's Web Presence · Accepted Answer · 2020-10-15 23:39:32Z

0

I tested this with the code below and it worked fine.

df = pd.DataFrame()
df['student_id'] = [1,2,3,4,5,6,7]
df['numberpost'] = [12,3,4,3,4,5,334]

plt.bar(x=df['student_id'],
        height=df['numberpost'])
plt.xticks(rotation = 45)
plt.show()

My guess is your dataframe does not contain data.

Have you checked to see if the df contains data?

I assume your con variable actually defines parameters (or you left them out for anonymity) as well?

Simply testing with df.head() will tell you if you have results.

edited Oct 15, 2020 at 23:39

answered Oct 15, 2020 at 23:11

Ray's Web Presence

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1 Comment

atiqah yusri Over a year ago

I tested using df.head(), I have data in my dataframe. about the con, yes I left them out for anonymity, This is the output when I tested using df.head() drive.google.com/file/d/1Ifg2R7-pmU_TVO6s6y4gebAYK9gcnisT/…

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