lets_plot.geom_density2d

lets_plot.geom_density2d(mapping=None, *, data=None, stat=None, position=None, show_legend=None, manual_key=None, sampling=None, tooltips=None, kernel=None, adjust=None, bw=None, n=None, bins=None, binwidth=None, color_by=None, **other_args)

Display density function contour.

By default, this geom uses coord_fixed(). However, this may not be the best choice when the values on the X/Y axis have significantly different magnitudes. In such cases, try using coord_cartesian().

Parameters:

mappingFeatureSpec

Set of aesthetic mappings created by aes() function. Aesthetic mappings describe the way that variables in the data are mapped to plot “aesthetics”.

datadict or Pandas or Polars DataFrame

The data to be displayed in this layer. If None, the default, the data is inherited from the plot data as specified in the call to ggplot.

statstr, default=’density2d’

The statistical transformation to use on the data for this layer, as a string.

positionstr or FeatureSpec, default=’identity’

Position adjustment. Either a position adjustment name: ‘dodge’, ‘dodgev’, ‘jitter’, ‘nudge’, ‘jitterdodge’, ‘fill’, ‘stack’ or ‘identity’, or the result of calling a position adjustment function (e.g., position_dodge() etc.).

show_legendbool, default=True

False - do not show legend for this layer.

manual_keystr or layer_key

The key to show in the manual legend. Specify text for the legend label or advanced settings using the layer_key() function.

samplingFeatureSpec

Result of the call to the sampling_xxx() function. To prevent any sampling for this layer pass value “none” (string “none”).

tooltipslayer_tooltips

Result of the call to the layer_tooltips() function. Specify appearance, style and content.

kernelstr, default=’gaussian’

The kernel we use to calculate the density function. Choose among ‘gaussian’, ‘cosine’, ‘optcosine’, ‘rectangular’ (or ‘uniform’), ‘triangular’, ‘biweight’ (or ‘quartic’), ‘epanechikov’ (or ‘parabolic’).

bwstr or list of float

The method (or exact value) of bandwidth. Either a string (choose among ‘nrd0’ and ‘nrd’), or a float array of length 2.

adjustfloat

Adjust the value of bandwidth by multiplying it. Change how smooth the frequency curve is.

nlist of int

The number of sampled points for plotting the function (on x and y direction correspondingly).

binsint

Number of levels.

binwidthfloat

Distance between levels.

color_by{‘fill’, ‘color’, ‘paint_a’, ‘paint_b’, ‘paint_c’}, default=’color’

Define the color aesthetic for the geometry.

other_args

Other arguments passed on to the layer. These are often aesthetics settings used to set an aesthetic to a fixed value, like color=’red’, fill=’blue’, size=3 or shape=21. They may also be parameters to the paired geom/stat.

Returns:

LayerSpec

Geom object specification.

Notes

Computed variables:

• ..group.. : number of density estimate contour line.

• ..level.. : calculated value of the density estimate for given contour line.

geom_density2d() understands the following aesthetics mappings:

• x : x-axis coordinates.

• y : y-axis coordinates.

• alpha : transparency level of a layer. Accept values between 0 and 1.

• color (colour) : color of the geometry lines. For more info see https://lets-plot.org/python/pages/aesthetics.html#color-and-fill.

• size : lines width.

• linetype : type of the line of border. Codes and names: 0 = ‘blank’, 1 = ‘solid’, 2 = ‘dashed’, 3 = ‘dotted’, 4 = ‘dotdash’, 5 = ‘longdash’, 6 = ‘twodash’. For more info see https://lets-plot.org/python/pages/aesthetics.html#line-types.

• weight : used by ‘density2d’ stat to compute weighted density.

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‘density2d’ statistical transformation combined with parameter value contour=False could be used to draw heatmaps (see the example below).

Examples

import numpy as np
from lets_plot import *
LetsPlot.setup_html()
n = 1000
np.random.seed(42)
x = np.random.normal(size=n)
y = np.random.normal(size=n)
ggplot({'x': x, 'y': y}, aes('x', 'y')) + \
    geom_density2d()

import numpy as np
from lets_plot import *
LetsPlot.setup_html()
n = 1000
np.random.seed(42)
x = np.random.normal(size=n)
y = np.random.normal(size=n)
ggplot({'x': x, 'y': y}, aes('x', 'y')) + \
    geom_density2d(aes(color='..group..'), size=1, show_legend=False) + \
    scale_color_brewer(type='seq', palette='GnBu', direction=-1)

import numpy as np
from lets_plot import *
LetsPlot.setup_html()
n = 1000
np.random.seed(42)
x = np.random.normal(size=n)
y = np.random.normal(size=n)
p = ggplot({'x': x, 'y': y}, aes('x', 'y'))
bunch = GGBunch()
for i, bw in enumerate([.2, .4]):
    for j, n in enumerate([16, 256]):
        bunch.add_plot(p + geom_density2d(kernel='epanechikov', bw=bw, n=n) + \
                           ggtitle('bw={0}, n={1}'.format(bw, n)),
                       j * 400, i * 400, 400, 400)
bunch.show()