Line Chart in Plotly

Last Updated: 08 Nov 2025

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Line charts connect data points with smooth or straight lines — ideal for time series, trends, stock prices, or sensor data.

Hinglish Tip: Line chart = "time ke saath change dikhao" — jaise heartbeat monitor. Interactive → zoom karo, hover karo!

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Basic Line Chart

import plotly.express as px

# Sample data
x = ['Jan', 'Feb', 'Mar', 'Apr', 'May']
y = [10, 15, 13, 18, 22]

fig = px.line(x=x, y=y, title="Basic Line Chart")
fig.show()

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Key Parameters in px.line()

Parameter	Values / Examples	Purpose
data_frame	df	Use Pandas DataFrame
x, y	Column names or lists	X-axis (time), Y-axis (value)
color	Column name	Different lines per category
line_dash	Column or 'dash', 'dot'	Dashed, dotted lines
markers	True, False	Show dots on data points
hover_data	['extra_col']	Extra info on hover
title	String	Chart title
labels	'y' : 'Sales (₹)'	Rename axes
render_mode	'svg' or 'webgl'	webgl = faster for 10k+ points

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Full Example

import plotly.express as px
import pandas as pd

# Sample sales data
df = pd.DataFrame({
    'Month': ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun'],
    'Product A': [100, 120, 110, 140, 160, 180],
    'Product B': [80, 90, 95, 85, 100, 110],
    'Region': ['North', 'North', 'North', 'South', 'South', 'South']
})

fig = px.line(
    df,
    x='Month',
    y=['Product A', 'Product B'],
    color='Region',
    markers=True,
    line_dash='Region',
    title='Monthly Sales: Product A vs B (North vs South)',
    labels={
        'value': 'Sales (₹ in Thousands)',
        'variable': 'Product'
    },
    hover_data={'Region': True}
)

fig.update_layout(
    legend_title="Region",
    hovermode='x unified',  # Shows all values at same x
    font=dict(size=12)
)

fig.show()

Hinglish Tip: hovermode='x unified' → ek hi x pe saare values dikhega — comparison easy!

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Add Fill Area (Area Chart)

fig = px.area(
    df, x='Month', y='Product A',
    title='Product A Sales (Filled Area)',
    labels={'Product A': 'Revenue'}
)
fig.show()

Use px.area() for filled line charts.

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Multiple Lines with graph_objects

import plotly.graph_objects as go

fig = go.Figure()

fig.add_trace(go.Scatter(
    x=df['Month'], y=df['Product A'],
    mode='lines+markers',
    name='Product A',
    line=dict(color='royalblue', width=3),
    marker=dict(size=10)
))

fig.add_trace(go.Scatter(
    x=df['Month'], y=df['Product B'],
    mode='lines',
    name='Product B',
    line=dict(color='firebrick', dash='dash')
))

fig.update_layout(
    title='Custom Line Chart with Graph Objects',
    xaxis_title='Month',
    yaxis_title='Sales',
    hovermode='x'
)

fig.show()

Hinglish Tip: mode='lines+markers' → line + dots = professionaly to read!

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Save Interactive Plot

# Interactive HTML
fig.write_html("sales_line_chart.html")

# Static Image (PNG, PDF)
fig.write_image("sales_line_chart.png", engine="kaleido", width=1000, height=600)

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Common Mistakes to Avoid

Mistake	Fix
No markers → hard to see points	Use markers=True
Too many lines → messy	Use line_dash + color wisely
Hover shows junk	Use hovermode='x unified'
Plot lags with big data	Use render_mode='webgl'

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