# Individual alpha values in scatter plot

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### Question :

Individual alpha values in scatter plot

I’m wondering if it is possible to have individual alpha values for each point to be plotted using the `scatter` function of Matplotlib. I need to plot a set of points, each one with its alpha value.

For example, I have this code to plot some points

``````def plot_singularities(points_x, p, alpha_point, file_path):
plt.figure()
plt.scatter(points_x, points_y, alpha=alpha_point)
plt.savefig(file_path + '.png', dpi=100)
plt.close()
``````

All my `points_x`, `points_y` and `alpha_point` have n values. However, I can’t assign an array to the `alpha` parameter in `scatter()`. How can I have a different alpha value for each point? I can loop and plot point by point with each specific alpha value, but this doesn’t seem like a good approach.

## Answer #1:

tcaswell’s suggestion is correct, you can do it like this:

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

x = np.arange(10)
y = np.arange(10)

alphas = np.linspace(0.1, 1, 10)
rgba_colors = np.zeros((10,4))
# for red the first column needs to be one
rgba_colors[:,0] = 1.0
# the fourth column needs to be your alphas
rgba_colors[:, 3] = alphas

plt.scatter(x, y, color=rgba_colors)
plt.show()
``````

## Answer #2:

You can use the color argument and a colormap with alpha.
`cmap` linearly increases the alpha value from 0 to 1.

``````import numpy as np
import matplotlib.pylab as plt
from matplotlib import colors

c='C0'

xs = np.arange(10)

fig, ax = plt.subplots(1, 1)
cmap = colors.LinearSegmentedColormap.from_list(
'incr_alpha', [(0, (*colors.to_rgb(c),0)), (1, c)])
ax.scatter(xs, xs, c=xs, cmap=cmap, ec=None, s=10**2)

plt.show()
``````