Btukfyl

import numpy as np

import matplotlib

matplotlib.rcParams['text.usetex'] = True

import matplotlib.pyplot as plt





t = np.linspace(0.0, 1.0, 100)

s = np.cos(4 * np.pi * t) + 2



fig, ax = plt.subplots(figsize=(6, 4), tight_layout=True)

ax.plot(t, s)



ax.set_xlabel(r'textbf{time (s)}')

ax.set_ylabel('itshape {Velocity (N{DEGREE SIGN}/sec)}', fontsize=16)

ax.set_title(r'TeX is Number $displaystylesum_{n=1}^infty'

             r'frac{-e^{ipi}}{2^n}$!', fontsize=16, color='r')

plt.show()

This is the Tex example on Matplotlib site.
But, I got this messauntimeError:

latex was not able to process the following string:

'\\itshape {Velocity (\\N{DEGREE SIGN}/sec)}'

Here is the full report generated by latex:

This is pdfTeX, Version 3.14159265-2.6-1.40.16 (TeX Live 2015/Debian) (preloaded format=latex)

 restricted write18 enabled.

entering extended mode

(/home/joshua/.cache/matplotlib/tex.cache/88a38ed565fe9aac24ebc44c9a0be443.tex

LaTeX2e <2016/02/01>

Babel <3.9q> and hyphenation patterns for 81 language(s) loaded.

(/usr/share/texlive/texmf-dist/tex/latex/base/article.cls

Document Class: article 2014/09/29 v1.4h Standard LaTeX document class

(/usr/share/texlive/texmf-dist/tex/latex/base/size10.clo))

(/usr/share/texlive/texmf-dist/tex/latex/type1cm/type1cm.sty)

(/usr/share/texlive/texmf-dist/tex/latex/base/textcomp.sty

(/usr/share/texlive/texmf-dist/tex/latex/base/ts1enc.def))

(/usr/share/texlive/texmf-dist/tex/latex/ucs/ucs.sty

(/usr/share/texlive/texmf-dist/tex/latex/ucs/data/uni-global.def))

(/usr/share/texlive/texmf-dist/tex/latex/base/inputenc.sty

(/usr/share/texlive/texmf-dist/tex/latex/ucs/utf8x.def))

(/usr/share/texlive/texmf-dist/tex/latex/geometry/geometry.sty

(/usr/share/texlive/texmf-dist/tex/latex/graphics/keyval.sty)

(/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifpdf.sty)

(/usr/share/texlive/texmf-dist/tex/generic/oberdiek/ifvtex.sty)

(/usr/share/texlive/texmf-dist/tex/generic/ifxetex/ifxetex.sty)



Package geometry Warning: Over-specification in `h'-direction.

    `width' (5058.9pt) is ignored.





Package geometry Warning: Over-specification in `v'-direction.

    `height' (5058.9pt) is ignored.



) (./88a38ed565fe9aac24ebc44c9a0be443.aux)

(/usr/share/texlive/texmf-dist/tex/latex/base/ts1cmr.fd)

(/usr/share/texlive/texmf-dist/tex/latex/ucs/ucsencs.def)

*geometry* driver: auto-detecting

*geometry* detected driver: dvips



LaTeX Font Warning: Font shape `OT1/cmss/m/it' in size <16> not available

(Font)              Font shape `OT1/cmss/m/sl' tried instead on input line 15.



! Undefined control sequence.

l.15 ...0.000000}{sffamily itshape {Velocity (N

                                                  {DEGREE SIGN}/sec)}}

No pages of output.

Transcript written on 88a38ed565fe9aac24ebc44c9a0be443.log.ge over and over.

Is there anyone to solve this problem?