How to rotate x-axis tick labels on matplotlib bar chart? Tried several approaches, none worked

Question

I cannot rotate the x tick labels on a matplotlib bar chart, so those labels currently overlap. I've done some matplotlib documentation reading as well as other reading, and tried different approaches, yet none have worked. From my understanding of things I've read, it seems that there's more than one way to implement a bar chart using matplotlib, and that I cannot rotate tick labels on all bar charts, only on bar charts made in certain way(s). Is that accurate? Is there a way to do the x-axis tick labels rotation on my bar chart?

(Quick overview of what I'm trying to do: I'm making a web application, that includes a bar chart. The bar chart I'm working on should display names of side effects of cancer medications on the x-axis, and percentages of occurrence of each of those side effects on the y-axis. The side effects labels are long, so they overlap, and that's why I'm trying to rotate them.)

Here is the python code:

import os
import matplotlib.pyplot as plt
import numpy as np
import mpld3
from matplotlib import *
from cs50 import SQL
from flask import Flask, flash, jsonify, redirect, render_template, 
request, session
from flask_session import Session
from tempfile import mkdtemp
from werkzeug.exceptions import default_exceptions, HTTPException, 
InternalServerError
import sqlite3


app = Flask(__name__)

app.config["TEMPLATES_AUTO_RELOAD"] = True

app.config["SESSION_FILE_DIR"] = mkdtemp()
app.config["SESSION_PERMANENT"] = False
app.config["SESSION_TYPE"] = "filesystem"
Session(app)

db = SQL("sqlite:///cancermeds.db")

@app.route("/", methods=["GET", "POST"])
def index():
    if request.method=="POST":

        selection = request.form.get("cancerlist")
        if selection == "breast cancer":
            rows = db.execute("SELECT * FROM 'breast cancer'")
            for row in rows:
                keys = list(row.keys())
                del keys[16:19]
                print(keys)
                values = list(row.values())
                del values[16:19]
                print(values)

                positions = 
   [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]

                fig, ax = plt.subplots()
                fig = plt.figure(figsize=(7,6))
                ax = plt.bar(keys, values, width=0.5)

                plt.xlabel("Side Effects")
                plt.xticks(positions, keys)
                plt.xticks(rotation=60)
                plt.ylabel("Percentages of Occurence of Side 
Effects")
                plt.title("Bar Chart showing Side Effects of Breast 
Cancer Medication(s) With Their Corrresponding Percentages Of 
Occurence")

                fig = ax[0].figure
                bar_chart = mpld3.fig_to_html(fig)

        return render_template("breastcancer.html", bar_chart = bar_chart)

    else:
        return render_template("index.html")


if __name__ == '__main__':
    app.run(debug=True)

The plt.xticks(rotation=60) line is meant to rotate the x-axis tick labels by 60 degrees (I just chose 60 degrees, no specific reason for that exact number). However, the labels do not rotate at all, but strangely the x-axis label called "Side Effects" disappears. When I remove the plt.xticks(rotation=60) line, the "Side Effects" label re-appears in its place.

Thank you for your help.

You will need to create a [mcve], such that people can run your code. Also you would need to make it clear if the output your are concerned about is the one from matplotlib or from mpld3. — ImportanceOfBeingErnest, Aug 06 '19 at 20:38

score 2 · Answer 1 · answered Aug 06 '19 at 20:59

2

You have a couple options. You can do this when setting xticklabels or using tick_params.

fig = pl.figure(figsize=(5, 5))
ax0 = fig.add_subplot(111)

ax0.bar(x, height=2)

ax0.set_xticklabels(yourLabels, rotation=60)

# alternatively
ax0.tick_params(rotation=60)

Of course, you have to specify what your tick labels should be.

On a side note, I do not make my figures the same way you do (as you see in the example), which may or may not influence how you change your figure.

answered Aug 06 '19 at 20:59

tnknepp

5,888
6
43
57

I'll try using your answer and see how things work. Thank you! – John Aug 06 '19 at 21:04
I haven't been able to successfully incorporate this method of making figures into my code. I just don't really understand it. Do you recommend any particular readings that can help guide me from the stage of making a figure, to the stage of transferring the figure to html, to be able to display the bar chart on a webpage? Thank you. – John Aug 06 '19 at 22:27
@JohnAbdelmalek I guess I don't see the issue. Perhaps if you answer ImportanceOfBeingErnest's questions and provide the MWE you can get more help. – tnknepp Aug 07 '19 at 13:47

How to rotate x-axis tick labels on matplotlib bar chart? Tried several approaches, none worked

1 Answers1