How to fill area between curve defined by series of control points and x-axis

Question

How to fill area between curve defined by series of control points and x-axis?

MWE:

    \documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{intersections}
\usetikzlibrary{calc}

\begin{document}

\begin{tikzpicture}
    \def\xmin{-30}
    \def\xmax{450}
    \def\ymin{-30}
    \def\ymax{150}
    \def\nula{55}
    \def\phase{2.2}
    \def\myscale{0.5}

        \begin{scope}[draw=black,line join=round,miter limit=4.00,line width=0.5pt, y=1pt,x=1pt, scale=\myscale]      
          \draw[->] (\xmin,\nula) -- (\xmax,\nula) node[right] {$t$} coordinate(x axis);
          \draw[->] (\phase,\ymin) -- (\phase,\ymax) node[left]  {$v(t)$} coordinate(y axis);
          \path[name path=fce1,draw=black,line join=round,even odd rule,line cap=butt,miter   
            limit=4.00] (2.2036044,23.21323707) .. controls
            (2.2036044,23.21323707)  and (7.1896734,29.00183707)  .. (11.896862,37.80963707)  .. controls
            (14.463984,42.61313707)  and (16.430404,45.91313707)  .. (19.958399,53.79007707)  .. controls
            (23.178819,60.98027707)  and (34.001913,68.16119707)  .. (44.701755,69.73912707)  .. controls
            (55.401595,71.31705707)  and (62.430335,112.41315707) .. (84.285711,112.14281707) .. controls
            (106.14109,111.87247707) and (131.61574,2.01243707)   .. (164.28572,1.78563707)   .. controls
            (196.9557,1.55883707)    and (217.37186,52.05023707)  .. (217.37186,52.05023707);    
        \end{scope} 
\end{tikzpicture}
\end{document}

I would like to fill the space between the x axis and the positive part of the curve (between two zero-crossing). I found a lot of examples, but I have not found in any convenient way. Therefore, I turn to the community for some advice.

Answer 1

Here are two ways with \MyPath representing your original path

1. Add begin and end points to your path that end on the x-axis:

   \draw (\phase,\nula) -- \MyPath -- (217.37186,\nula)
   

   Everything is done in one step this way. However this method yields and additional draws which are probably not desired.

2. First fill the region, and then draw it:

     \fill [fill=yellow!10] (\phase,\nula) -- \MyPath -- (217.37186,\nula);
     \draw \MyPath;
   

   which yields:

   

   I would recommend method #2.

Code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{intersections}
\usetikzlibrary{calc}

\newcommand{\MyPath}{%
            (2.2036044,23.21323707) .. controls
            (2.2036044,23.21323707)  and (7.1896734,29.00183707)  .. 
            (11.896862,37.80963707)  .. controls
            (14.463984,42.61313707)  and (16.430404,45.91313707)  .. 
            (19.958399,53.79007707)  .. controls
            (23.178819,60.98027707)  and (34.001913,68.16119707)  .. 
            (44.701755,69.73912707)  .. controls
            (55.401595,71.31705707)  and (62.430335,112.41315707) .. 
            (84.285711,112.14281707) .. controls
            (106.14109,111.87247707) and (131.61574,2.01243707)   .. 
            (164.28572,1.78563707)   .. controls
            (196.9557,1.55883707)    and (217.37186,52.05023707)  .. 
            (217.37186,52.05023707)
}%

\begin{document}

\def\xmin{-30}
\def\xmax{450}
\def\ymin{-30}
\def\ymax{150}
\def\nula{55}
\def\phase{2.2}
\def\myscale{0.5}


\begin{tikzpicture}
        \begin{scope}[draw=black,line join=round,miter limit=4.00,line width=0.5pt, y=1pt,x=1pt, scale=\myscale]      

          \path[fill=yellow!10, name path=fce1,draw=black,line join=round,even odd rule,line cap=butt,miter   
            limit=4.00] 
            (\phase,\nula) -- \MyPath -- (217.37186,\nula);    

          \draw[->] (\xmin,\nula) -- (\xmax,\nula) node[right] {$t$} coordinate(x axis);
          \draw[->] (\phase,\ymin) -- (\phase,\ymax) node[left]  {$v(t)$} coordinate(y axis);
        \end{scope} 
\end{tikzpicture}

\begin{tikzpicture}
        \begin{scope}[draw=black,line join=round,miter limit=4.00,line width=0.5pt, y=1pt,x=1pt, scale=\myscale]      

\fill [fill=yellow!10] (\phase,\nula) -- \MyPath -- (217.37186,\nula);
          \path[name path=fce1,draw=black,line join=round,even odd rule,line cap=butt,miter   
            limit=4.00] 
          \MyPath;    

          \draw[->] (\xmin,\nula) -- (\xmax,\nula) node[right] {$t$} coordinate(x axis);
          \draw[->] (\phase,\ymin) -- (\phase,\ymax) node[left]  {$v(t)$} coordinate(y axis);
        \end{scope} 
\end{tikzpicture}
\end{document}
\end{document}