# TexLive TikZ Graphics

**TikZ** is a powerful drawing package for creating diagrams, flowcharts, plots, and graphics programmatically. Load with `\usepackage{tikz}`. Drawings are created inside `tikzpicture` environments using commands that specify paths, shapes, and styling.

Basic drawing uses coordinates and paths. A path connects points with straight lines or curves. `\draw` renders lines; `\fill` fills shapes; `\node` places text.

```latex
\documentclass{standalone}
\usepackage{tikz}
\begin{document}

\begin{tikzpicture}
  \draw (0,0) -- (2,0) -- (2,1) -- (0,1) -- cycle;
  \node at (1, 0.5) {Rectangle};
\end{tikzpicture}

\end{document}
```

This draws a rectangle from (0,0) to (2,1) with "Rectangle" centered inside. `cycle` closes the path back to the start. Coordinates are in centimeters by default.

**Circles and ellipses:**

```latex
\begin{tikzpicture}
  \draw (1,1) circle (0.5);           % circle at (1,1) with radius 0.5cm
  \draw (3,1) ellipse (1cm and 0.5cm); % ellipse (horizontal and vertical radii)
  \fill[blue] (5,1) circle (0.3);     % filled circle
\end{tikzpicture}
```

**Styling** uses options in square brackets: color, line width, fill, etc.

```latex
\begin{tikzpicture}
  \draw[thick, red] (0,0) -- (2,0);
  \draw[line width=2pt, blue] (0,1) -- (2,1);
  \fill[green] (1,2) circle (0.3);
  \draw[dashed] (0,3) -- (2,3);
\end{tikzpicture}
```

**Arrows and nodes:**

```latex
\begin{tikzpicture}[node distance=2cm]
  \node (A) at (0,0) {A};
  \node (B) at (2,0) {B};
  \draw[->] (A) -- (B);  % arrow from A to B
  \draw[<->] (A) to[bend left=30] (B); % curved arrow
\end{tikzpicture}
```

The `->` makes arrowheads; `<->` makes double-headed arrows. `to[bend left=30]` curves the line; adjust the angle to curve more or less.

**Grids and axes** are useful for plots:

```latex
\begin{tikzpicture}
  \draw[gray, thin] (0,0) grid (4,3);
  \draw[->] (-0.5,0) -- (4,0) node[right] {$x$};
  \draw[->] (0,-0.5) -- (0,3) node[above] {$y$};
  \draw[blue, thick] (0,0) -- (2,2) -- (4,1);
\end{tikzpicture}
```

The grid provides reference lines. Nodes on arrow ends label axes.

**Plot functions:**

```latex
\begin{tikzpicture}
  \draw[gray, thin] (0,0) grid (4,2);
  \draw[blue, thick, domain=0:4] plot (\x, {sin(\x * 180 / pi)});
\end{tikzpicture}
```

`plot` draws a function. `domain=0:4` sets the x-range. Use `\x` for the variable; wrap expressions in `{...}`. Trig functions use degrees, so multiply radians by `180/pi`.

**Flowcharts** combine rectangles and arrows:

```latex
\begin{tikzpicture}[node distance=2cm]
  \node[rectangle, draw] (start) {Start};
  \node[rectangle, draw, below of=start] (process) {Process};
  \node[diamond, draw, below of=process] (decision) {Decision};
  \draw[->] (start) -- (process);
  \draw[->] (process) -- (decision);
\end{tikzpicture}
```

Node shapes: `rectangle`, `circle`, `ellipse`, `diamond`. The `[below of=...]` option positions relative to another node.

**Standalone documents** compile TikZ drawings independently. Use `\documentclass{standalone}` instead of `article`:

```latex
\documentclass{standalone}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
  \draw (0,0) circle (1);
\end{tikzpicture}
\end{document}
```

This produces a PDF sized exactly to fit the drawing—no extra margins. Useful for creating graphics to include in other documents with `\includegraphics`.

TikZ is complex but powerful. Start with simple paths and shapes, then explore advanced features (graphs, matrix layouts, 3D projections) as needed. Read the [TikZ manual](http://mirrors.ctan.org/graphics/pgf/base/doc/pgfmanual.pdf) for comprehensive documentation.