scatter plot error - possibly data type - TypeError: nan is not a string

[chudson]

plt.scatter(DialogUsers.TRDAT, DialogUsers.ERDAT)
plt.show()

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-3277b90008cc> in <module>()
----> 1 plt.scatter(DialogUsers.TRDAT, DialogUsers.ERDAT)
      2 plt.show()

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\pyplot.py in scatter(x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, hold, data, **kwargs)
   3473                          vmin=vmin, vmax=vmax, alpha=alpha,
   3474                          linewidths=linewidths, verts=verts,
-> 3475                          edgecolors=edgecolors, data=data, **kwargs)
   3476     finally:
   3477         ax._hold = washold

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\__init__.py in inner(ax, *args, **kwargs)
   1865                         "the Matplotlib list!)" % (label_namer, func.__name__),
   1866                         RuntimeWarning, stacklevel=2)
-> 1867             return func(ax, *args, **kwargs)
   1868 
   1869         inner.__doc__ = _add_data_doc(inner.__doc__,

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\axes\_axes.py in scatter(self, x, y, s, c, marker, cmap, norm, vmin, vmax, alpha, linewidths, verts, edgecolors, **kwargs)
   4245             edgecolors = 'face'
   4246 
-> 4247         self._process_unit_info(xdata=x, ydata=y, kwargs=kwargs)
   4248         x = self.convert_xunits(x)
   4249         y = self.convert_yunits(y)

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\axes\_base.py in _process_unit_info(self, xdata, ydata, kwargs)
   2170             # we only need to update if there is nothing set yet.
   2171             if not self.yaxis.have_units():
-> 2172                 self.yaxis.update_units(ydata)
   2173 
   2174         # process kwargs 2nd since these will override default units

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\axis.py in update_units(self, data)
   1467         neednew = self.converter != converter
   1468         self.converter = converter
-> 1469         default = self.converter.default_units(data, self)
   1470         if default is not None and self.units is None:
   1471             self.set_units(default)

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\category.py in default_units(data, axis)
    113         # default_units->axis_info->convert
    114         if axis.units is None:
--> 115             axis.set_units(UnitData(data))
    116         else:
    117             axis.units.update(data)

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\category.py in __init__(self, data)
    180         self._counter = itertools.count(start=0)
    181         if data is not None:
--> 182             self.update(data)
    183 
    184     def update(self, data):

~\AppData\Local\Continuum\anaconda3\lib\site-packages\matplotlib\category.py in update(self, data)
    199         for val in OrderedDict.fromkeys(data):
    200             if not isinstance(val, VALID_TYPES):
--> 201                 raise TypeError("{val!r} is not a string".format(val=val))
    202             if val not in self._mapping:
    203                 self._mapping[val] = next(self._counter)

TypeError: nan is not a string