`mpl_to_plotly` does not preserve axis labels (bar plots are useless)

[krassowski]

While mpl_to_plotly is little known and receives little love, this bug is pretty easy to fix. Would you be open to a PR?

import matplotlib.pyplot as plt
from plotly.tools import mpl_to_plotly
from plotly.offline import plot

In matplotlib this produces a barplot with labels:

labels = ['a', 'b', 'c']
values = [1, 2, 3]

f = plt.figure(figsize=(6, 4))
plt.bar(labels, values)
plt.tight_layout()

But conversion to plotly looses the labels:

plotly_fig = mpl_to_plotly(f)
plot(plotly_fig)

A minimal fix would be to modify prep_ticks by appending:

    if axis_dict.get("type") == "date":
        return axis_dict
    
    vals = []
    texts = []
    for tick in axis.majorTicks:
        vals.append(tick.get_loc())
        texts.append(tick.label1.get_text())
    
    if texts:
        axis_dict = {}
        axis_dict['tickmode'] = 'array'
        axis_dict['tickvals'] = vals
        axis_dict['ticktext'] = texts
    
    return axis_dict

which produces:

prep_ticks is defined in:

plotly.py/plotly/matplotlylib/mpltools.py

Lines 428 to 514 in c54a2bd

	def prep_ticks(ax, index, ax_type, props):
	"""Prepare axis obj belonging to axes obj.
	positional arguments:
	ax - the mpl axes instance
	index - the index of the axis in `props`
	ax_type - 'x' or 'y' (for now)
	props - an mplexporter poperties dictionary
	"""
	axis_dict = dict()
	if ax_type == "x":
	axis = ax.get_xaxis()
	elif ax_type == "y":
	axis = ax.get_yaxis()
	else:
	return dict() # whoops!
	scale = props["axes"][index]["scale"]
	if scale == "linear":
	# get tick location information
	try:
	tickvalues = props["axes"][index]["tickvalues"]
	tick0 = tickvalues[0]
	dticks = [
	round(tickvalues[i] - tickvalues[i - 1], 12)
	for i in range(1, len(tickvalues) - 1)
	]
	if all([dticks[i] == dticks[i - 1] for i in range(1, len(dticks) - 1)]):
	dtick = tickvalues[1] - tickvalues[0]
	else:
	warnings.warn(
	"'linear' {0}-axis tick spacing not even, "
	"ignoring mpl tick formatting.".format(ax_type)
	)
	raise TypeError
	except (IndexError, TypeError):
	axis_dict["nticks"] = props["axes"][index]["nticks"]
	else:
	axis_dict["tick0"] = tick0
	axis_dict["dtick"] = dtick
	axis_dict["tickmode"] = None
	elif scale == "log":
	try:
	axis_dict["tick0"] = props["axes"][index]["tickvalues"][0]
	axis_dict["dtick"] = (
	props["axes"][index]["tickvalues"][1]
	- props["axes"][index]["tickvalues"][0]
	)
	axis_dict["tickmode"] = None
	except (IndexError, TypeError):
	axis_dict = dict(nticks=props["axes"][index]["nticks"])
	base = axis.get_transform().base
	if base == 10:
	if ax_type == "x":
	axis_dict["range"] = [
	math.log10(props["xlim"][0]),
	math.log10(props["xlim"][1]),
	]
	elif ax_type == "y":
	axis_dict["range"] = [
	math.log10(props["ylim"][0]),
	math.log10(props["ylim"][1]),
	]
	else:
	axis_dict = dict(range=None, type="linear")
	warnings.warn(
	"Converted non-base10 {0}-axis log scale to 'linear'" "".format(ax_type)
	)
	else:
	return dict()
	# get tick label formatting information
	formatter = axis.get_major_formatter().__class__.__name__
	if ax_type == "x" and "DateFormatter" in formatter:
	axis_dict["type"] = "date"
	try:
	axis_dict["tick0"] = mpl_dates_to_datestrings(axis_dict["tick0"], formatter)
	except KeyError:
	pass
	finally:
	axis_dict.pop("dtick", None)
	axis_dict.pop("tickmode", None)
	axis_dict["range"] = mpl_dates_to_datestrings(props["xlim"], formatter)
	if formatter == "LogFormatterMathtext":
	axis_dict["exponentformat"] = "e"
	return axis_dict

[gvwilson]

thanks very much @krassowski - yes, we would be very happy to get a PR. thanks - @gvwilson