# Set Marker Size of Scatter Plot in Matplotlib

Suraj Joshi Apr 12, 2021

The size of scatter markers in Matplotlib is specified by the `s` keyword argument of the function `scatter()`, where `s` is a scalar or an array.

## `s` Keyword Argument to Set Matplotlib Scatter Marker Size

The Syntax of the `scatter` function:

``````matplotlib.pyplot.scatter(
x,
y,
s=None,
c="b",
marker="o",
cmap=None,
norm=None,
vmin=None,
vmax=None,
alpha=None,
linewidths=None,
faceted=True,
verts=None,
hold=None,
**kwargs
)
``````

Where, `s` is a scalar or an array of the same length as `x` and `y`, to set the scatter marker size. The default scatter marker size is `rcParams['lines.markersize'] ** 2`. According to documentation, `s` is the marker size in points2.

## Set the Same Scatter Marker Size of All Points in Matplotlib

``````import numpy as np
import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = np.sin(x)

plt.scatter(x, y, s=500, c="magenta")

plt.title("Scatter plot of sinx")
plt.xlabel("x")
plt.ylabel("sinx")
plt.xlim(0, 6)
plt.ylim(-2, 2)
plt.show()
``````

## Increase Scatter Marker Size of Points Non-Uniformly in Matplotlib

### Double the Width of Matplotlib Scatter Marker

To double the `width` (or `height`) of the marker we need to increase `s` by a factor of `4` as `A = W*H => (2W)*(2H)= 4A`.

``````import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [a ** 2 for a in x]
s = [10 * 4 ** n for n in range(len(x))]
plt.scatter(x, y, s=s)
plt.title("Doubling width of marker in scatter plot")
plt.xlabel("x")
plt.ylabel("x**2")
plt.xlim(0, 6)
plt.ylim(0, 30)
plt.show()
``````

### Double the Area of Matplotlib Scatter Marker

To double the area of the marker, we increase the `area` by a factor of `2`, so the marker size scales linearly with the `area`.

``````import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [a ** 2 for a in x]
s = [10 * 2 ** n for n in range(len(x))]
plt.scatter(x, y, s=s)
plt.title("Doubling area of marker in scatter plot")
plt.xlabel("x")
plt.ylabel("x**2")
plt.xlim(0, 6)
plt.ylim(0, 30)
plt.show()
``````

## `markersize` Parameter to Set Scatter Marker Size in Matplotlib `plot` Function

``````import matplotlib.pyplot as plt

x = [1, 2, 3, 4, 5]
y = [0] * len(x)

plt.plot(x, y, "bo", markersize=10)
plt.show()
``````

Here the area of the circle is controlled by the `markersize` parameter.

Author: Suraj Joshi

Suraj Joshi is a backend software engineer at Matrice.ai.