Draw Points in drawn coordinate system

pgfplotstikz-pgf

I would like to produce a graph like I attached.

I started with drawing a coordinate system and adding 3 points, to create a triangle, but the reference is not the origin of the coordinate system… How could I get the attached graph?

 \begin{center}
 \begin{tikzpicture}
 \begin{axis}[
  %Same unit length
  axis equal,
  scale=1.5,
  transform shape,
  axis lines=middle,
  axis line style={Stealth-Stealth, thick},
  xmin=-8.5,xmax=8.5,ymin=-8.5,ymax=8.5,
  xtick distance=1,
  ytick distance=1,
  xlabel=$x$,
  ylabel=$y$,
  title={},
  grid=both,
  grid style={line width=.1pt, draw=darkgray!10},
  major grid style={line width=.2pt,draw=darkgray!50},
  axis lines=middle,
  %For plot of functions domain
  domain = -8:8
  ]

\addplot[blue] {-1/2*x} node[above,pos=1] {};
\addplot[red] {2*x} node[above,pos=1] {};

\draw (10,8) node[anchor=north] {a}
  -- (13,8) node[anchor=north]{b}
  -- (18,14) node[anchor=south]{c}
  -- cycle;


\end{axis}
\end{tikzpicture}
\end{center}

Best Answer

Since you seem to not know anything about TikZ yet, here's a simple solution without any fancy tricks, with straightforward commands that you may learn from. Note that this is not the best way to do that but one may start with something simple.

\documentclass[tikz,border=3.14mm]{standalone}

\begin{document}
    \begin{tikzpicture}[font=\sffamily\small]
        \draw[gray!50,very thin] (-5,-4) grid (5,4);
        \draw[thick,-latex] (-5,0) -- (5,0) node [below left] {x};
        \draw[thick,-latex] (0,-4) -- (0,4) node [below left] {y};
        
        \foreach \x in {-4,...,-1,1,2,3,4} \draw (\x,2pt) --++ (0,-4pt) node [below] {\x};
        \foreach \y in {-3,...,-1,1,2,3} \draw (2pt,\y) --++ (-4pt,0) node [left] {\y};

        \fill[cyan, fill opacity=0.5] (0,0) -- (0,2) node [right, pos=0.6, red, opacity=1] {$\Delta$x} -- (-1,2) node [above, pos=0.5, blue, opacity=1] {$\Delta$y} -- cycle;
        
        \fill[violet, fill opacity=0.5] (0,0) -- (2,0) node [below, pos=0.75, red, opacity=1] {$\Delta$x} -- (2,1) node [right, pos=0.5, blue, opacity=1] {$\Delta$y} -- cycle;
        
        \fill[red, fill opacity=0.5] (0,0) -- (-153:0.8) arc(-153:-63:0.8) node[pos=0.5, above] {90$^{\circ}$} -- cycle;
        \begin{scope}
            \clip (-5,-4) rectangle (5,4);  
            \draw[line width=1pt,olive,domain=(-5:5)] plot (\x,-2*\x);
            \node[olive, above] at (-1.4,3) {g};
            
            \draw[line width=1pt,blue!50!cyan,domain=(-5:5)] plot (\x,0.5*\x);      
            \node[blue!50!cyan, above left] at (4,2) {f};
        \end{scope}
    \end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] How to hide empty (value 0) ybars with pgfplots

You can use

 y filter/.expression={y==0 ? nan : y}

in the options of \addplot.

\documentclass{article}

% ---------------------------------- tikz
\usepackage{pgfplots}          % to print charts
\pgfplotsset{compat=1.12}

\begin{document}

\begin{figure}
  \centering
  \begin{tikzpicture}
    \begin{axis} [
      % general
      ybar,
      scale only axis,
      height=0.5\textwidth,
      width=1.2\textwidth,
      ylabel={\# Dots},
      nodes near coords,
      xlabel={Variation},
      xticklabel style={
        rotate=90,
        anchor=east,
      },
      %enlarge x limits={abs value={3}},
      ]
      \addplot+[y filter/.expression={y==0 ? nan : y}] table [
        x=grade,
        y=value,
      ] {
grade   value
-11 0
-10 0
-9  0
-8  0
-7  0
-6  0
-5  3
-4  1
-3  2
-2  15
-1  11
0   179
1   8
2   1
3   0
4   1
5   2
6   0
7   0
8   0
9   0
10  0
11  0
      };
    \end{axis}
  \end{tikzpicture}
\end{figure}
\end{document}

[Tex/LaTex] Line up nested tikz enviroments or how to get rid of them

As is explained in How do I draw shapes inside a tikz node? pics can be used for defining new objects. My main problem using pics is how to place where you want because they aren't nodes and positioning them is not so easy.

Following code shows how to define EDFA block.

    EDFA/.pic={
        \begin{scope}[scale=.5]
        \draw (-1,0) coordinate (in) --  (-1,1) -- (1,0) coordinate (out) --  (-1,-1) -- cycle;
        \node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
        \end{scope}

In this case, coordinate (-1,0) will act as west anchor and 1,0 as east. Both point will have an special name for further reference. Every pic is placed according its own origin (0,0). You can use Claudio's answer to Anchoring TiKZ pics for better positioning.

As your example was simple, I'd prefer to star with EDFA and place Source and Sink after it.

\documentclass[]{article}

% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning

\begin{document}

\tikzset{%
    EDFA/.pic={
        \begin{scope}[scale=.5]
        \draw (-1,0) coordinate (in) --  (-1,1) -- (1,0) coordinate (out) --  (-1,-1) -- cycle;
        \node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
        \end{scope}
    }
}

\begin{tikzpicture}[
block/.style={draw},
]

\draw pic (edfa) {EDFA};

\node[block, left=of edfain] (source) {Source};

\node[block, right= of edfaout] (sink) {Sink};

\draw[->] (source) -- (edfain);
\draw[->] (edfaout) -- (sink);

\end{tikzpicture}

\end{document}

I understand that your components are more complex than EDFA because for this particular case an isosceles triangle node with a label will do the work and it can be used as a node and not as a pic:

\documentclass[]{article}

% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning
\usetikzlibrary{shapes.geometric}

\begin{document}

\begin{tikzpicture}[
    block/.style={draw},
    edfa/.style={isosceles triangle, minimum width=1cm, 
         draw, anchor=west, isosceles triangle stretches, 
         minimum height=1cm, label=-80:#1}
]

\node[block] (source) {Source};

\node[edfa=1, right=of source] (edfa) {};

\node[block, right= of edfa] (sink) {Sink};

\draw[->] (source) -- (edfa);
\draw[->] (edfa) -- (sink);

\end{tikzpicture}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] How to hide empty (value 0) ybars with pgfplots

[Tex/LaTex] Line up nested tikz enviroments or how to get rid of them

Related Question