Line Graph
Chart overview
Line graphs are fundamental visualizations for displaying continuous data and trends over time.
Key points
- By connecting data points with lines, they effectively communicate the direction and rate of change in your data.
- Multiple lines can be used to compare trends across different categories, making line graphs ideal for stock prices, temperature changes, sales trends, and any time-series analysis.
Python Tutorial
How to create a line graph in Python
Use the full tutorial for implementation details, troubleshooting, and chart variations in matplotlib, seaborn, and plotly.
How to Plot Time Series Data in PythonExample Visualization

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View example prompt
"Create a multi-line graph comparing 'Monthly Average Temperature' for 3 cities (New York, Miami, Chicago) over a full year (Jan-Dec). Generate realistic data: New York (30°F-85°F), Miami (65°F-90°F), Chicago (25°F-80°F) with appropriate seasonal patterns. Use distinct line colors (NYC: blue, Miami: orange, Chicago: green) and marker styles (circle, square, diamond). Add a shaded region showing the 'comfortable range' (60-75°F). Include grid lines, format Y-axis with °F, add month abbreviations on X-axis. Title the chart professionally, add a legend positioned outside the plot, and annotate the hottest and coldest points for each city."
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Python Code Example
# === IMPORTS ===
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
from datetime import datetime
# === USER-EDITABLE PARAMETERS ===
x_col = 'Date' # Change: column name for x-axis (datetime)
y_col = 'Temperature' # Change: column name for y-axis (numeric)
group_col = 'City' # Change: column name for grouping variable
figsize = (12, 6) # Change: figure size in inches
title_fontsize = 18 # Change: title font size
label_fontsize = 16 # Change: axis label and tick font size
colors = ['#1f77b4', '#ff7f0e', '#2ca02c'] # Change: hex colors for each city
markers = ['o', 's', '^'] # Change: markers for each city
line_width = 2 # Change: line width
show_legend = True # Change: whether to show legend
# === DATA PREPARATION ===
# Generate example dataset: monthly average temperatures for 3 cities over one year
np.random.seed(0)
months = pd.date_range(start='2023-01-01', periods=12, freq='MS')
cities = ['City A', 'City B', 'City C']
data = []
for city in cities:
if city == 'City A':
base = 20
trend = 5
elif city == 'City B':
base = 15
trend = 3
else: # City C
base = 10
trend = 1
temps = base + trend * np.sin(np.linspace(0, 2*np.pi, 12)) + np.random.normal(0, 2, 12)
for date, temp in zip(months, temps):
data.append({'Date': date, 'City': city, 'Temperature': temp})
df = pd.DataFrame(data)
# === ANALYSIS ===
# Compute max temperature per city
max_temps = df.groupby(group_col)[y_col].max()
max_months = df.loc[df.groupby(group_col)[y_col].idxmax()][['Date', group_col, y_col]]
mean_temps = df.groupby(group_col)[y_col].mean()
# Print analysis results
print("Maximum temperatures per city:")
for city in cities:
month_str = max_months.loc[max_months[group_col]==city, 'Date'].dt.strftime('%b %Y').values[0]
print(f" {city}: {max_temps[city]:.1f}°C on {month_str}")
print("\nMean temperatures per city:")
for city in cities:
print(f" {city}: {mean_temps[city]:.1f}°C")
# Determine city with highest max temperature for title
top_city = max_temps.idxmax()
top_temp = max_temps[top_city]
top_month = max_months.loc[max_months[group_col]==top_city, 'Date'].dt.strftime('%b').values[0]
# === PLOT CREATION ===
fig, ax = plt.subplots(figsize=figsize)
# Plot each city's temperature trend
for i, city in enumerate(cities):
city_data = df[df[group_col]==city].sort_values(x_col)
ax.plot(city_data[x_col], city_data[y_col],
label=city,
color=colors[i],
marker=markers[i],
linewidth=line_width,
markersize=6)
# Formatting
ax.set_title(f"{top_city} reaches highest temperatures of {top_temp:.1f}°C in {top_month}",
fontsize=title_fontsize)
ax.set_xlabel('Month', fontsize=label_fontsize)
ax.set_ylabel('Temperature (°C)', fontsize=label_fontsize)
ax.tick_params(axis='both', which='major', labelsize=label_fontsize)
# Legend
if show_legend:
ax.legend(loc='upper left', fontsize=label_fontsize)
# Annotation of max temperatures
max_temps_str = ', '.join([f"{city}: {max_temps[city]:.1f}°C" for city in cities])
ax.text(0.95, 0.85, f"Max temps: {max_temps_str}",
transform=ax.transAxes,
ha='right', va='top',
bbox=dict(boxstyle='round', facecolor='white', alpha=0.8))
# Layout adjustments
plt.subplots_adjust(top=0.90, bottom=0.12, left=0.12, right=0.95)
plt.tight_layout()
# Display plot
plt.show()
# END-OF-CODEOpens the Analyze page with this code pre-loaded and ready to execute
Console Output
Annual Temperature Statistics: New York: min=30°F, max=82°F, avg=54.6°F Miami: min=65°F, max=90°F, avg=79.8°F Chicago: min=25°F, max=80°F, avg=52.3°F Comfortable Months (60-75°F): NYC=7, Miami=4, Chicago=5
Common Use Cases
- 1Stock price tracking over time
- 2Website traffic analysis
- 3Temperature and weather trends
- 4Sales performance comparison
Pro Tips
Use distinct colors and markers for multiple series
Consider adding a legend outside the plot area
Highlight important data points or events
Long-tail keyword opportunities
High-intent chart variations
Library comparison for this chart
matplotlib
Best when you need full control over axis formatting, annotation placement, and journal-specific styling for line-graph.
seaborn
Fastest path to statistically-aware defaults and tidy-data workflows, especially for grouped and distribution-focused line-graph views.
plotly
Best for interactive hover, zoom, and web sharing when collaborators need to inspect values directly from line-graph figures.
Scientific Chart Selection Cheat Sheet
Not sure whether to use a Violin Plot, Box Plot, or Ridge Plot? Download our single-page reference mapping the most-used scientific chart types, exactly when to use them, and the core Matplotlib/Seaborn functions.