Plot Viewer#

import param
import panel as pn

from bokeh.sampledata.iris import flowers
from panel.viewable import Viewer

import hvplot.pandas

This example demonstrates the use of a Viewer class to build a reactive app. It uses the iris dataset which is a standard example used to illustrate machine-learning and visualization techniques.

We will start by using the dataframe with these five features and then create a Selector parameter to develop menu options for different input features. Later we will define the core plotting function in a plot method and define the layout in the __panel__ method of the IrisDashboard class.

The plot method watches the X_variable and Y_variable using the param.depends decorator. The plot method plots the features selected for X_variable and Y_variable and colors them using the species column.

inputs = ['sepal_length', 'sepal_width', 'petal_length', 'petal_width']

class IrisDashboard(Viewer):
    X_variable = param.Selector(objects=inputs, default=inputs[0])
    Y_variable = param.Selector(objects=inputs, default=inputs[1])

    @param.depends('X_variable', 'Y_variable')
    def plot(self):
        return flowers.hvplot.scatter(x=self.X_variable, y=self.Y_variable, by='species').opts(height=600)

    def __panel__(self):
        return pn.Row(
            pn.Param(self, width=300, name="Plot Settings"),