Make rescale_discrete_levels a plot option

[maximlt]

It was a datashader operation option, it's now a plot option that has no default value, like cnorm.

I assumed holoviz/holoviews#5268 would be merged, setting rescale_discrete_levels to True by default in the shader operation. If not, and if the intent is to have it set by default to True in hvPlot but not in HoloViews (I'd prefer them having the same default), this PR will have to be adapted.

import numpy as np, pandas as pd
import hvplot.pandas

def random_walk(n, f=5000):
    """Random walk in a 2D space, smoothed with a filter of length f"""
    xs = np.convolve(np.random.normal(0, 0.1, size=n), np.ones(f)/f).cumsum()
    ys = np.convolve(np.random.normal(0, 0.1, size=n), np.ones(f)/f).cumsum()
    xs += 0.1*np.sin(0.1*np.array(range(n-1+f))) # add wobble on x axis
    xs += np.random.normal(0, 0.005, size=n-1+f) # add measurement noise
    ys += np.random.normal(0, 0.005, size=n-1+f)
    return np.column_stack([xs, ys])

paths = random_walk(2000,30)
df = pd.DataFrame(paths, columns=['x', 'y'])

df.hvplot.paths(x='x', y='y', aspect=1, datashade=True, cnorm='eq_hist') + \
df.hvplot.paths(x='x', y='y', aspect=1, rasterize=True, cnorm='eq_hist')

[jbednar]

Thanks. I think this is ready to merge, along with the corresponding HoloViews PR.

[philippjfr]

Thanks!