Hello,

I am going through the quickstart titled "An Example: Building a Price Network" found here https://graph-tool.skewed.de/static/doc/quickstart.html#an-example-building-a-price-network

After running the program, I receive the following output which is different from what the quickstart suggests should be output. Here is what I get:

------

vertex: 36063 in-degree: 0 out-degree: 1 age: 36063
vertex: 9075 in-degree: 4 out-degree: 1 age: 9075
vertex: 5967 in-degree: 3 out-degree: 1 age: 5967
vertex: 1113 in-degree: 7 out-degree: 1 age: 1113
vertex: 25 in-degree: 84 out-degree: 1 age: 25
vertex: 10 in-degree: 541 out-degree: 1 age: 10
vertex: 5 in-degree: 140 out-degree: 1 age: 5
vertex: 2 in-degree: 362 out-degree: 1 age: 2
vertex: 0 in-degree: 636 out-degree: 0 age: 0
Nowhere else to go... We found the main hub!

-----

The output from "vertex: 36063 ..." down to "vertex: 5 ..." is as expected, but at "vertex: 2 ..." onward is different, and I am receiving the following error message, and the plot fails to be drawn

"ValueError: 'yerr' must not contain negative values"

The full error output is as follows

--------------

ValueError                                Traceback (most recent call last)
Cell In [2], line 92
     89 err[err >= y] = y[err >= y] - 1e-2
     91 figure(figsize=(6,4))
---> 92 errorbar(in_hist[1][:-1], in_hist[0], fmt="o", yerr=err,
     93         label="in")
     94 gca().set_yscale("log")
     95 gca().set_xscale("log")

File ~/anaconda3/envs/rapids-2208/lib/python3.8/site-packages/matplotlib/pyplot.py:2480, in errorbar(x, y, yerr, xerr, fmt, ecolor, elinewidth, capsize, barsabove, lolims, uplims, xlolims, xuplims, errorevery, capthick, data, **kwargs)
   2474 @_copy_docstring_and_deprecators(Axes.errorbar)
   2475 def errorbar(
   2476         x, y, yerr=None, xerr=None, fmt='', ecolor=None,
   2477         elinewidth=None, capsize=None, barsabove=False, lolims=False,
   2478         uplims=False, xlolims=False, xuplims=False, errorevery=1,
   2479         capthick=None, *, data=None, **kwargs):
-> 2480     return gca().errorbar(
   2481         x, y, yerr=yerr, xerr=xerr, fmt=fmt, ecolor=ecolor,
   2482         elinewidth=elinewidth, capsize=capsize, barsabove=barsabove,
   2483         lolims=lolims, uplims=uplims, xlolims=xlolims,
   2484         xuplims=xuplims, errorevery=errorevery, capthick=capthick,
   2485         **({"data": data} if data is not None else {}), **kwargs)

File ~/anaconda3/envs/rapids-2208/lib/python3.8/site-packages/matplotlib/__init__.py:1423, in _preprocess_data.<locals>.inner(ax, data, *args, **kwargs)
   1420 @functools.wraps(func)
   1421 def inner(ax, *args, data=None, **kwargs):
   1422     if data is None:
-> 1423         return func(ax, *map(sanitize_sequence, args), **kwargs)
   1425     bound = new_sig.bind(ax, *args, **kwargs)
   1426     auto_label = (bound.arguments.get(label_namer)
   1427                   or bound.kwargs.get(label_namer))

File ~/anaconda3/envs/rapids-2208/lib/python3.8/site-packages/matplotlib/axes/_axes.py:3587, in Axes.errorbar(self, x, y, yerr, xerr, fmt, ecolor, elinewidth, capsize, barsabove, lolims, uplims, xlolims, xuplims, errorevery, capthick, **kwargs)
   3584 res = np.zeros(err.shape, dtype=bool)  # Default in case of nan
   3585 if np.any(np.less(err, -err, out=res, where=(err == err))):
   3586     # like err<0, but also works for timedelta and nan.
-> 3587     raise ValueError(
   3588         f"'{dep_axis}err' must not contain negative values")
   3589 # This is like
   3590 #     elow, ehigh = np.broadcast_to(...)
   3591 #     return dep - elow * ~lolims, dep + ehigh * ~uplims
   3592 # except that broadcast_to would strip units.
   3593 low, high = dep + np.row_stack([-(1 - lolims), 1 - uplims]) * err

ValueError: 'yerr' must not contain negative values

-------------------------

Any idea as to what the issue might be? I am running Python 3.8, Matplotlib 3.6.0, and graph-tool 2.45

Apologies for the previous message for the wrong library to this list, I am testing out a few libraries and hastily sent that message to the wrong project.