""" ================================================ Kernel Density Estimate of Species Distributions ================================================ This shows an example of a neighbors-based query (in particular a kernel density estimate) on geospatial data, using a Ball Tree built upon the Haversine distance metric -- i.e. distances over points in latitude/longitude. The dataset is provided by Phillips et. al. (2006). If available, the example uses `basemap `_ to plot the coast lines and national boundaries of South America. This example does not perform any learning over the data (see :ref:`sphx_glr_auto_examples_applications_plot_species_distribution_modeling.py` for an example of classification based on the attributes in this dataset). It simply shows the kernel density estimate of observed data points in geospatial coordinates. The two species are: - `"Bradypus variegatus" `_ , the Brown-throated Sloth. - `"Microryzomys minutus" `_ , also known as the Forest Small Rice Rat, a rodent that lives in Peru, Colombia, Ecuador, Peru, and Venezuela. References ---------- - `"Maximum entropy modeling of species geographic distributions" `_ S. J. Phillips, R. P. Anderson, R. E. Schapire - Ecological Modelling, 190:231-259, 2006. """ # noqa: E501 # Authors: The scikit-learn developers # SPDX-License-Identifier: BSD-3-Clause import matplotlib.pyplot as plt import numpy as np from sklearn.datasets import fetch_species_distributions from sklearn.neighbors import KernelDensity # if basemap is available, we'll use it. # otherwise, we'll improvise later... try: from mpl_toolkits.basemap import Basemap basemap = True except ImportError: basemap = False def construct_grids(batch): """Construct the map grid from the batch object Parameters ---------- batch : Batch object The object returned by :func:`fetch_species_distributions` Returns ------- (xgrid, ygrid) : 1-D arrays The grid corresponding to the values in batch.coverages """ # x,y coordinates for corner cells xmin = batch.x_left_lower_corner + batch.grid_size xmax = xmin + (batch.Nx * batch.grid_size) ymin = batch.y_left_lower_corner + batch.grid_size ymax = ymin + (batch.Ny * batch.grid_size) # x coordinates of the grid cells xgrid = np.arange(xmin, xmax, batch.grid_size) # y coordinates of the grid cells ygrid = np.arange(ymin, ymax, batch.grid_size) return (xgrid, ygrid) # Get matrices/arrays of species IDs and locations data = fetch_species_distributions() species_names = ["Bradypus Variegatus", "Microryzomys Minutus"] Xtrain = np.vstack([data["train"]["dd lat"], data["train"]["dd long"]]).T ytrain = np.array( [d.decode("ascii").startswith("micro") for d in data["train"]["species"]], dtype="int", ) Xtrain *= np.pi / 180.0 # Convert lat/long to radians # Set up the data grid for the contour plot xgrid, ygrid = construct_grids(data) X, Y = np.meshgrid(xgrid[::5], ygrid[::5][::-1]) land_reference = data.coverages[6][::5, ::5] land_mask = (land_reference > -9999).ravel() xy = np.vstack([Y.ravel(), X.ravel()]).T xy = xy[land_mask] xy *= np.pi / 180.0 # Plot map of South America with distributions of each species fig = plt.figure() fig.subplots_adjust(left=0.05, right=0.95, wspace=0.05) for i in range(2): plt.subplot(1, 2, i + 1) # construct a kernel density estimate of the distribution print(" - computing KDE in spherical coordinates") kde = KernelDensity( bandwidth=0.04, metric="haversine", kernel="gaussian", algorithm="ball_tree" ) kde.fit(Xtrain[ytrain == i]) # evaluate only on the land: -9999 indicates ocean Z = np.full(land_mask.shape[0], -9999, dtype="int") Z[land_mask] = np.exp(kde.score_samples(xy)) Z = Z.reshape(X.shape) # plot contours of the density levels = np.linspace(0, Z.max(), 25) plt.contourf(X, Y, Z, levels=levels, cmap=plt.cm.Reds) if basemap: print(" - plot coastlines using basemap") m = Basemap( projection="cyl", llcrnrlat=Y.min(), urcrnrlat=Y.max(), llcrnrlon=X.min(), urcrnrlon=X.max(), resolution="c", ) m.drawcoastlines() m.drawcountries() else: print(" - plot coastlines from coverage") plt.contour( X, Y, land_reference, levels=[-9998], colors="k", linestyles="solid" ) plt.xticks([]) plt.yticks([]) plt.title(species_names[i]) plt.show()