[Tex/LaTex] Coloring a node after its creation

nodestikz-pgf

I want to fill a node with a specific color, but not with the usual [fill=blue] way. The reason is, that I am creating many many nodes and I want to fill some random nodes with a different color from the others, so the coloring can not be embedded in the creation process. Any ideas?

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric,%
decorations.pathreplacing,decorations.pathmorphing,shapes,%
matrix,shapes.symbols}

\begin{document}
\begin{tikzpicture}[darkstyle/.style={circle,draw,fill=gray!20,minimum size=20}]


  \foreach \x in {0,...,2}
    \foreach \y in {0,...,2} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
       \node [darkstyle]  (\x\y) at (1.5*\x,1.5*\y) {};} 

  \foreach \x in {0,...,2}
    \foreach \y [count=\yi] in {0,...,1}  
      \draw (\x\y)--(\x\yi)  ;


\draw [decorate,decoration={brace,amplitude=7pt,raise=2pt,aspect=0.5}] (20.south) -- (00.south); 

  \foreach \x in {0,...,2}
    \foreach \y in {0,...,3} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
       \node [darkstyle]  (\x\y) at (10+1.5*\x,1.5*\y) {};} 

  \foreach \x in {0,...,2}
    \foreach \y [count=\yi] in {0,...,2}  
      \draw (\x\y)--(\x\yi)  ;

\draw [decorate,decoration={brace,amplitude=7pt,raise=2pt,aspect=0.5}] (20.south) -- (00.south); 



  \foreach \x in {0,...,5}
    \foreach \y in {0,...,4} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
       \node [darkstyle]  (\x\y) at (3+1.5*\x,-10+1.5*\y) {};} 

  \foreach \x in {0,...,5}
    \foreach \y [count=\yi] in {0,...,3}  
      \draw (\x\y)--(\x\yi)  ;



\end{tikzpicture}
\end{document}

Lets say we want to fill with blue color the top leftmost node and the bottom rightmost node.

Best Answer

enter image description here

\documentclass{minimal}
\usepackage{tikz}
\usetikzlibrary{calc,trees,positioning,arrows,chains,shapes.geometric,%
decorations.pathreplacing,decorations.pathmorphing,shapes,%
matrix,shapes.symbols}

\begin{document}
\begin{tikzpicture}[
darkstyle/.style={circle,draw,fill=gray!20,minimum size=20},
bluestyle/.style={circle,draw,fill=blue!20,minimum size=20},
]


  \foreach \x in {0,...,2}
    \foreach \y in {0,...,2} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
\ifnum\x=\ifnum\y=2 0\else-1\fi
       \node [bluestyle]  (\x\y) at (1.5*\x,1.5*\y) {};
\else
       \node [darkstyle]  (\x\y) at (1.5*\x,1.5*\y) {};
\fi
       } 

  \foreach \x in {0,...,2}
    \foreach \y [count=\yi] in {0,...,1}  
      \draw (\x\y)--(\x\yi)  ;


\draw [decorate,decoration={brace,amplitude=7pt,raise=2pt,aspect=0.5}] (20.south) -- (00.south); 

  \foreach \x in {0,...,2}
    \foreach \y in {0,...,3} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
       \node [darkstyle]  (\x\y) at (10+1.5*\x,1.5*\y) {};} 

  \foreach \x in {0,...,2}
    \foreach \y [count=\yi] in {0,...,2}  
      \draw (\x\y)--(\x\yi)  ;

\draw [decorate,decoration={brace,amplitude=7pt,raise=2pt,aspect=0.5}] (20.south) -- (00.south); 



  \foreach \x in {0,...,5}
    \foreach \y in {0,...,4} 
       {\pgfmathtruncatemacro{\label}{\x - 5 *  \y +21}
\ifnum\x=\ifnum\y=0 5\else-1\fi
       \node [bluestyle]  (\x\y) at (3+1.5*\x,-10+1.5*\y) {};
\else
       \node [darkstyle]  (\x\y) at (3+1.5*\x,-10+1.5*\y) {};
\fi

} 

  \foreach \x in {0,...,5}
    \foreach \y [count=\yi] in {0,...,3}  
      \draw (\x\y)--(\x\yi)  ;



\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] TikZ: Omit {} after \node declaration for unlabelled node

The node contents option can be used instead of the curley braces.

You can apply it to all nodes:

\documentclass{article}

\usepackage{tikz}

\tikzset{
    every node/.append style = {
        node contents =,
    },
}

\begin{document}
    \begin{tikzpicture}
        \node[fill=red];
    \end{tikzpicture}
\end{document}

Or you can define a custom style that you apply to all nodes in question:

\documentclass{article}

\usepackage{tikz}

\tikzset{
    notext/.style = {
        node contents =,
    },
}

\begin{document}
    \begin{tikzpicture}
        \node[notext, fill=red];
    \end{tikzpicture}
\end{document}

See TikZ documentation page 215.

Please note that "When the option [node contents] is used inside the options of a node, the parsing of the node stops immediately after the end of the option block."

But it is still possible to name a node with the name option.

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

Best Answer

Related Solutions

[Tex/LaTex] TikZ: Omit {} after \node declaration for unlabelled node

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

Related Question