Peeling off the layers

This example uses thresholds to select two different ranges of values in the data, and display them on the same scatter plot using a lower opacity for the outer layer, revealing the inside of the clusters.

import plopp as pp
import scipp as sc
import numpy as np

We first generate some fake data, meant to represent clusters of points in a three-dimensional space.

The data values scale with \(1/r^{2}\) where \(r\) is the distance to the center of each cluster.

from plopp.data.examples import clusters3d

da = clusters3d()

We select two data ranges (high values and low values), and display both at the same time, lowering the opacity of the low-value data range.

# Select ranges
a = da[da.data > sc.scalar(0.05)]
b = da[(da.data > sc.scalar(0.002)) & (da.data < sc.scalar(0.005))]

# Display both on the same scatter plot
p = pp.scatter3d({'a': a, 'b': b}, pos='position', norm='log')

# Extract the point clouds from the final plot and set a lower opacity on the second point cloud
clouds = list(p.artists.values())
clouds[1].opacity = 0.1

p