# How to draw this z-grid graph of constant damping factors and natural frequencies pt2

This question is building from the elegant solution given by marsupilam found here:

How to draw this z-grid graph of constant damping factors and natural frequencies

How to plot the other have of this plot (from marsupilam's code given below), so that the new plot is a full circle like this:

Here is his super code:

\documentclass[12pt,tikz,border=2pt]{standalone}
\usepackage{pgfplots}
\usepgfplotslibrary{polar}

\begin{document}
\begin{tikzpicture}
\begin{axis}
[
height=15cm,
unit vector ratio = 1 1,
ymin=0,
xmax=1.1,
ymax=1.1,
samples=100,
axis lines=center,
ticks=none,
]

\pgfplotsinvokeforeach{0,...,9}
{
\def\zet{(.1*#1)}
\pgfmathsetmacro{\factor}{\zet/sqrt(1-\zet^2)}
node[at end, sloped, anchor=south,font=\tiny, inner sep=0pt] {$\zeta{=}0.#1$};
}

\pgfplotsinvokeforeach{.1,.2,...,1}
{
\def\a{#1}
}
\end{axis}
\end{tikzpicture}
\end{document}

• could you also please paste the other question's URL in the body of this question? You don't need to add it as a link. The system will automatically prettify it in a few seconds. – percusse Jun 5 '17 at 8:47

This seems to do the trick...

1. there is one line missing, that for zeta=1. I suggest you draw it by hand.
2. I am not sure about the values of zeta in the lower part, maybe 1/0.9, 1/0.8, and so on ?

## The code

\documentclass[12pt,tikz,border=2pt]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.14}
\usepgfplotslibrary{polar}

\begin{document}
\begin{tikzpicture}
\begin{axis}
[
height=15cm,
unit vector ratio = 1 1,
xmin=-1.05,
xmax=1.1,
ymin=-1.1,
ymax=1.1,
samples=100,
%axis lines=center,
%ticks=none,
minor tick num=4,
xtick distance=.25,
ytick distance=.1,
major grid style={thick},
xticklabels={,-1,,-0.5,,0,,0.5,,1},
yticklabels={,0,,0.2,,0.4,,0.6,,0.8,,1},
grid=both,
]

\pgfplotsinvokeforeach{0,...,9}
{
\def\zet{(.1*#1)}
\pgfmathsetmacro{\factor}{\zet/sqrt(1-\zet^2)}
node [at end, sloped, anchor=south,font=\tiny, inner sep=0pt, fill=white,]{$\zeta{=}0.#1$};
node [at end, sloped, anchor=north,font=\tiny, inner sep=2pt, fill=white,]{$\zeta{=}-0.#1$};
}

\pgfplotsinvokeforeach{.1,.2,...,1}
{
\def\a{#1}