Tex plots, using pgfplots. Non-numeric characters on axes.

\begin{figure}[htbp]\begin{center} % plot. Z is changed by complex amounts. No good.
\mbox{
\tikzstyle{every axis legend}+= [at={(0.98,0.98)},anchor=north east] % im is 0,0 to 1,1
\begin{tikzpicture}
\begin{axis}[width=\plotw,height=\ploth,
xlabel={$x/l$}, ylabel={$\theta$},grid=major,
ytick ={0, 0.79, 1.57, 2.36, 3.14, 3.93, 4.71, 5.50, 6.28},
yticklabels={0, , , , $\pi$, , , ,$2 \pi$},
xmin = -0.1, xmax = 1.1, ymin=0, ymax=6.28]

% reference.dumptex(r1[0] / 0.02, reference.ang(r1[1]))
% 1000 Hz, 0 flow

\addplot[color = black] plot coordinates {(0.00000e+00,4.71241e+00) (5.00000e-02,4.69414e+00) (1.00000e-01,4.67588e+00) (1.50000e-01,4.65761e+00) (2.00000e-01,4.63934e+00) (2.50000e-01,4.62109e+00) (3.00000e-01,4.60281e+00) (3.50000e-01,4.58455e+00) (4.00000e-01,4.56629e+00) (4.50000e-01,4.54803e+00) (5.00000e-01,4.52976e+00) (5.50000e-01,4.51149e+00) (6.00000e-01,4.49323e+00) (6.50000e-01,4.47496e+00) (7.00000e-01,4.45670e+00) (7.50000e-01,4.43843e+00) (8.00000e-01,4.42016e+00) (8.50000e-01,4.40191e+00) (9.00000e-01,4.38364e+00) (9.50000e-01,4.36537e+00) (1.00000e+00,4.34711e+00)};

\legend{Phase.\\}

\end{axis} \end{tikzpicture}

}
\caption{Zero flow, one-dimensional results at $f=1kHz$.}
\label{fig:m95acou2a_pvf} \end{center} \end{figure}