Log axis when plotting holoviews object through datashader

With the following code I’m trying to maintain the log scale of the x-axis which seems to work when using the pure holoview plot (top plot), but not when plotting the holoview.NdOverlay object through the datashader (bottom plot).

import numpy as np
import holoviews as hv
import datashader as ds
from holoviews.operation.datashader import datashade, dynspread
hv.extension('bokeh')

%%opts NdOverlay  [height=256 width=1024 show_grid=True logx=True]
%%opts RGB [height=256 width=1024 show_grid=True logx=True]

frequencies = [0.5, 0.75, 1.0, 1.25]
def sine_curve(phase, freq):
    xvals = [0.1*i+.0001 for i in range(100)]
    return hv.Curve((xvals, [np.sin(phase+freq*x) for x in xvals]))
overlay = hv.NdOverlay({f: sine_curve(0, f) for f in frequencies}, kdims='channel_keys')
curve_plot = dynspread(datashade(overlay, aggregator=ds.count_cat('channel_keys')))
(overlay + curve_plot).cols(1)

[wmayner]

Just got bitten by this. Maybe in the interim it would make sense to throw a warning until a proper fix can be implemented? Right now, it fails silently and could mislead users into thinking they’re looking at the log scaled plot when they actually aren’t.

[jbednar]

Yes, I agree. I don’t quite know how to detect this case cleanly, but if it’s obvious to anyone else, I’d be very happy to see a PR appear that warns or even raises an exception (given how unlikely it is that someone would find the current behavior useful or appropriate).