Line_chart_with_plotly

In this file I will explain how to use plotly with markers and annotation. It is very easy to plot chart in plotly express!:)

Let’s create two datasets: they include sales & anomalies for the first 10 days of Jan 2023.

# create dataset
import pandas as pd
df = pd.DataFrame({"Date": ["2023-01-01", "2023-01-02", "2023-01-03", "2023-01-04", "2023-01-05", "2023-01-06", "2023-01-07", 
              "2023-01-08", "2023-01-09", "2023-01-10"],
     "Analysis": ["Normal", "Anomaly", "Normal", "Anomaly", "Anomaly", "Normal", "Normal", "Normal", "Normal", "Normal"],
     "Sales": [120, 30, 115, 10, 5, 100, 99, 123, 134, 96]})

We need to convert the “date” to datetime to show it in x axis properly.

# to datetime
df.Date = pd.to_datetime(df.Date)
df_with_group.Date = pd.to_datetime(df_with_group.Date)

Here is a simple way to plot a animation chart!

import plotly.express as px
fig = px.line(df, x="Date", y="Sales", title='Daily Sales')
fig.show()

Now it is time to mark the anomalies! We will use Graph objects for this. Start with mark the anomaly dates:

anomaly_date = df[df.Analysis == "Anomaly"]

It is required to import graph objects to mark “anomalies”.

import plotly.graph_objects as go
fig = px.line(df, x="Date", y="Sales", title='Daily Sales')
fig.add_traces(go.Scatter(x=anomaly_date["Date"], y=anomaly_date["Sales"], mode="markers", name="Anomaly", 
                          hoverinfo="skip"))
fig.show(renderer='notebook')

If you want to see the “Anomaly” as a string on the chart, you should use “add_annotation”:

fig = px.line(df, x="Date", y="Sales", title='Daily Sales')
fig.add_traces(go.Scatter(x=anomaly_date["Date"], y=anomaly_date["Sales"], mode="markers", name="Anomaly", 
                          hoverinfo="skip"))
for idx in range(len(anomaly_date)):
     fig.add_annotation(dict(font=dict(color='rgba(0,0,200,0.8)',size=12),
                                        x=anomaly_date["Date"].iloc[idx],
                                        y=anomaly_date["Sales"].iloc[idx],
                                        showarrow=False,
                                        text=anomaly_date["Analysis"].iloc[idx],
                                        textangle=0,
                                        xanchor='auto',  #['auto', 'left', 'center', 'right']
                                        xref="x",
                                        yref="y"))
fig.show()

How to embed plotly chart to md file?

It is a bit tricky when you want to publish your plotly express plots as md file. In this blog I’m using Jeykll and mostly, I prefer to convert my jupyter notebooks to html and publish them directly. However, when it comes to publish plotly there are many erros in github deployment. For example: Liquid syntax error

First, I tried to solve this problem by my own with this function:

def prepend_string(filename, string):
    with open(filename, 'r+') as f:
        content = f.read()
        f.seek(0, 0)
        f.write(string.rstrip('\r\n') + '\n' + content)
        f.seek(15038, 0)
        f.write(string.replace("}", "}}"))
        f.seek(13617, 0)
        f.write(string.replace("}", "}}"))
        f.seek(13611, 0)
        f.write(string.replace("}", "}}"))

Unfortunately the error continues with new lines. I know this is not the right / proper way to deal with html files, but I try anyway:)

Then I gave up converting jupyter notebook to html, and instead, I’ve decided to create an md file which you’re reaaing now:)

I used jupyter notebook to create the plots and save the charts. Following function is used for saving plotly express as html file:

import plotly.express as px
import plotly.io as pio
fig = px.line(df, x="Date", y="Sales", title='Daily Sales')
fig.show()
pio.write_html(fig, file='plotly_simple.html', auto_open=False)

I moved those html files to _includes folder. In order to show the plot in the md file you can simply add a line:

include html

References

• https://raw.githubusercontent.com/plotly/plotly.py/master/doc/python/line-and-scatter.md
• https://stackoverflow.com/questions/60513164/display-interactive-plotly-chart-html-file-on-github-pages
• https://stackoverflow.com/questions/64241461/plotly-how-to-add-markers-at-specific-points-in-plotly-line-graph-python-pan
• https://stackoverflow.com/questions/68731627/plotly-express-line-chart-mark-specific-points-and-retain-hover-data
• https://davistownsend.github.io/blog/PlotlyBloggingTutorial/