Markers

Markers highlight individual data points on a line plot.

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Basic Marker Usage

Add markers with the marker parameter:

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-5, 5, 10)
y = np.sin(x)

fig, ax = plt.subplots()
ax.plot(x, y, marker='o')
plt.show()

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Common Marker Types

Marker	Description
'o'	Circle
's'	Square
'^'	Triangle up
'v'	Triangle down
'*'	Star
'+'	Plus
'x'	X
'D'	Diamond
'p'	Pentagon
'H'	Hexagon
'.'	Point
','	Pixel

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Marker Size (markersize / ms)

Control marker size:

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-5, 5, 5)
y = np.sin(x)

fig, ax = plt.subplots()
ax.plot(x, y, marker='p', markersize=15)
plt.show()

Short form:

ax.plot(x, y, marker='p', ms=15)

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Marker Colors

Edge color (markeredgecolor / mec):

ax.plot(x, y, marker='o', markeredgecolor='red')
# Short: mec='red'

Face color (markerfacecolor / mfc):

ax.plot(x, y, marker='o', markerfacecolor='blue')
# Short: mfc='blue'

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Marker Edge Width (markeredgewidth / mew)

Control the thickness of the marker border:

ax.plot(x, y, marker='o', markeredgewidth=4)
# Short: mew=4

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Complete Marker Customization

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-5, 5, 5)
y = np.sin(x)

fig, ax = plt.subplots()
ax.plot(x, y,
        marker='p',           # Pentagon marker
        markersize=15,        # Size
        markeredgecolor='red',   # Edge color
        markeredgewidth=4,    # Edge width
        markerfacecolor='blue')  # Fill color
plt.show()

Short form:

ax.plot(x, y, marker='p', ms=15, mec='red', mew=4, mfc='blue')

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MATLAB-Style Format Strings

Combine marker with line and color:

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(-2*np.pi, 2*np.pi, 10)
y = np.sin(x)

plt.plot(x, y, '--*r', ms=20)  # dashed line, star marker, red
plt.show()

Common combinations:

• '-o': solid line with circles
• '--s': dashed line with squares
• ':^': dotted line with triangles
• '-.D': dash-dot line with diamonds

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Comprehensive Example

import matplotlib.pyplot as plt
import numpy as np

x = [1, 2, 3]
y = [1, 5, 2]

plt.plot(x, y, 
         ls="--",       # Line style
         c='k',         # Color (black)
         marker="H",    # Hexagon marker
         ms=20,         # Marker size
         mec="r",       # Edge color (red)
         mfc="b",       # Face color (blue)
         mew=4,         # Edge width
         lw=5,          # Line width
         alpha=0.5)     # Transparency
plt.show()

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Markers Without Lines

Use empty line style to show only markers:

import matplotlib.pyplot as plt
import numpy as np

x = np.random.rand(20)
y = np.random.rand(20)

plt.plot(x, y, 'o', ms=10)  # Only circles, no line
plt.show()

Or explicitly:

plt.plot(x, y, marker='o', linestyle='', ms=10)

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Marker Every N Points

For dense data, mark every nth point:

import matplotlib.pyplot as plt
import numpy as np

x = np.linspace(0, 10, 100)
y = np.sin(x)

plt.plot(x, y, marker='o', markevery=10)  # Mark every 10th point
plt.show()

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Key Takeaways

• marker sets the marker type ('o', 's', '*', etc.)
• markersize (ms) controls size
• markeredgecolor (mec) sets border color
• markerfacecolor (mfc) sets fill color
• markeredgewidth (mew) sets border thickness
• Format strings combine marker, line, and color: '--or'
• Use markevery for dense data