[Tex/LaTex] tikz: draw multicolor curve with smooth gradient

colorgradienttikz-pgf

Yes, I know there are several topics about, but no one referred to my case. While colormap seems works only with plots, how can I draw a multicolor curve with smooth gradient? This is my attempt:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{makecell}
\setcellgapes{5pt}
\usepackage{booktabs}
\usepackage{amsmath,amssymb,amsfonts,systeme,mathtools} 
\usepackage{pgfplots}
\usepackage{float}

\begin{document}

\begin{figure}[H]
\centering
\begin{tikzpicture}
  \begin{axis}[
  ticks=none,
  grid=none,
  xmin=0,xmax=100,
  ymin=0,ymax=100,
  axis lines = middle,
  set layers,
  xlabel={$t$},ylabel={$T$},
  x label style={at={(1,0)},right},
  y label style={at={(0,1)},above},
  colormap={redblue}{rgb255(0cm)=(255,0,0); rgb255(1cm)=(0,0,255)}
               ]
    \draw [ultra thick] (20,90) to[out=270,in=110] (25,60) to[out=335,in=115] (35,45) to[out=0,in=180] (70,45) to[out=305,in=150] (90,20);
    \node[inner sep=0pt, label={[outer sep=-2pt]45:A}] at (20,90) {} ;
    \node[label={[outer sep=-2pt]45:B}] at (25,60) {} ;
    \node[label={[outer sep=-2pt]45:C}] at (35,45) {} ;
    \node[label={[outer sep=-2pt]45:D}] at (70,45) {} ;
    \node[label={[outer sep=-2pt]45:E}] at (90,20) {} ;
    \addplot[only marks, mark options={solid,draw=green,fill=green}]
    coordinates {
    (20,90) (25,60) (35,45) (70,45) (90,20)
    };
    \end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

Can you help me?

Thank you in advance

Best Answer

As you said, colormaps works with plots. In your code there is indeed a plot, but only for plotting the marks and hence not the line. This one is drawn with the \draw command inside the axis. Therefore, you have to add a gradient color to your line.

Gradient with two colors

For instance, using the solution by Mark Wibrow to How to draw an arrow with two colors? you can add a color gradient using \path and the defined shading path option in tikset. Then with left color=<color> and right color=<color> (or top color=<color> and bottom color=<color>) you have a gradient with only two colors.

Output:

Code:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{makecell}
\setcellgapes{5pt}
\usepackage{booktabs}
\usepackage{amsmath,amssymb,amsfonts,systeme,mathtools} 
\usepackage{pgfplots}
\usepackage{float}
\usetikzlibrary{decorations.markings,fadings}

%https://tex.stackexchange.com/questions/137357/how-to-draw-an-arrow-with-two-colors
\makeatletter
\newif\iftikz@shading@path

\tikzset{
    % There are three circumstances in which the fading sep is needed:
    % 1. Arrows which do not update the bounding box (which is most of them).
    % 2. Line caps/joins and mitres that extend outside the natural bounding 
    %    box of the path (these are not calculated by PGF).
    % 3. Other reasons that haven't been anticipated.
    fading xsep/.store in=\pgfpathfadingxsep,
    fading ysep/.store in=\pgfpathfadingysep,
    fading sep/.style={fading xsep=#1, fading ysep=#1},
    fading sep=0.0cm,
    shading path/.code={%
        % Prevent this stuff happning recursively.
        \iftikz@shading@path%
        \else%
        \tikz@shading@pathtrue%
        % \tikz@addmode installs the `modes' (e.g., fill, draw, shade) 
        % to be applied to the path. It isn't usualy for doing more
        % changes to the path's construction.
        \tikz@addmode{%
            \pgfgetpath\pgf@currentfadingpath%
            % Get the boudning box of the current path size including the fading sep
            \pgfextract@process\pgf@fadingpath@southwest{\pgfpointadd{\pgfqpoint{\pgf@pathminx}{\pgf@pathminy}}%
                {\pgfpoint{-\pgfpathfadingxsep}{-\pgfpathfadingysep}}}%%
            \pgfextract@process\pgf@fadingpath@northeast{\pgfpointadd{\pgfqpoint{\pgf@pathmaxx}{\pgf@pathmaxy}}%
                {\pgfpoint{\pgfpathfadingxsep}{\pgfpathfadingysep}}}%
            % Clear the path
            \pgfsetpath\pgfutil@empty%                          
            % Interrupt the path and picture to create a fading.
            \pgfinterruptpath%
            \pgfinterruptpicture%
            \begin{tikzfadingfrompicture}[name=.]
                \path [shade=none,fill=none, #1] \pgfextra{%
                    % Set the softpath. Any transformations in #1 will have no effect.
                    % This will *not* update the bounding box...
                    \pgfsetpath\pgf@currentfadingpath%
                    % ...so it is done manually.
                    \pgf@fadingpath@southwest
                    \expandafter\pgf@protocolsizes{\the\pgf@x}{\the\pgf@y}%
                    \pgf@fadingpath@northeast%
                    \expandafter\pgf@protocolsizes{\the\pgf@x}{\the\pgf@y}%
                };
                % Now get the bounding of the picture.
                \xdef\pgf@fadingboundingbox@southwest{\noexpand\pgfqpoint{\the\pgf@picminx}{\the\pgf@picminy}}%
                \xdef\pgf@fadingboundingbox@northeast{\noexpand\pgfqpoint{\the\pgf@picmaxx}{\the\pgf@picmaxy}}%
                %
            \end{tikzfadingfrompicture}%
            \endpgfinterruptpicture%
            \endpgfinterruptpath%
            % Install a rectangle that covers the shaded/faded path picture.                                
            \pgfpathrectanglecorners{\pgf@fadingboundingbox@southwest}{\pgf@fadingboundingbox@northeast}%
            % Make the fading happen.
            \def\tikz@path@fading{.}%
            \tikz@mode@fade@pathtrue%
            \tikz@fade@adjustfalse%10pt
            % Shift the fading to the mid point of the rectangle
            \pgfpointscale{0.5}{\pgfpointadd{\pgf@fadingboundingbox@southwest}{\pgf@fadingboundingbox@northeast}}%
            \edef\tikz@fade@transform{shift={(\the\pgf@x,\the\pgf@y)}}%
        }%
        \fi%
    }
}


\begin{document}

\begin{figure}[H]
\centering
\begin{tikzpicture}
  \begin{axis}[
  ticks=none,
  grid=none,
  xmin=0,xmax=100,
  ymin=0,ymax=100,
  axis lines = middle,
  set layers,
  xlabel={$t$},ylabel={$T$},
  x label style={at={(1,0)},right},
  y label style={at={(0,1)},above},
  %colormap={redblue}{rgb255(0cm)=(255,0,0); rgb255(1cm)=(0,0,255)}
               ]
    \path [left color=red, right color=blue, shading path={draw=transparent!0, ultra thick,}]
    (20,90) to[out=270,in=110] (25,60) to[out=335,in=115] (35,45) to[out=0,in=180] (70,45) to[out=305,in=150] (90,20);
%    \draw [ultra thick] (20,90) to[out=270,in=110] (25,60) to[out=335,in=115] (35,45) to[out=0,in=180] (70,45) to[out=305,in=150] (90,20);
    \node[inner sep=0pt, label={[outer sep=-2pt]45:A}] at (20,90) {} ;
    \node[label={[outer sep=-2pt]45:B}] at (25,60) {} ;
    \node[label={[outer sep=-2pt]45:C}] at (35,45) {} ;
    \node[label={[outer sep=-2pt]45:D}] at (70,45) {} ;
    \node[label={[outer sep=-2pt]45:E}] at (90,20) {} ;
    \addplot[only marks, mark options={solid,draw=green,fill=green}]
    coordinates {
    (20,90) (25,60) (35,45) (70,45) (90,20)
    };
    \end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

Gradient with multicolors

For a multicolor gradient there is also a possibility. The aforementioned solution pass a gradient of two colors to the line color with the commands of the Shading library (Chapter 69, p.737). Therefore, if we are able to pass a multicolor gradient to Mark Wibrow´s solution, we have it done. Thankfully, Mark Wibrow gives us also the solution in the answer to How to draw gradient arrows with Tikz. Just combining both of them we can set a desired multicolor gradient.

Output with shading1:

Output with shading2:

Output with shading3:

Code:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{makecell}
\setcellgapes{5pt}
\usepackage{booktabs}
\usepackage{amsmath,amssymb,amsfonts,systeme,mathtools} 
\usepackage{pgfplots}
\usepackage{float}
\usetikzlibrary{decorations.markings,fadings}

%https://tex.stackexchange.com/questions/137357/how-to-draw-an-arrow-with-two-colors
\makeatletter
\newif\iftikz@shading@path

\tikzset{
    % There are three circumstances in which the fading sep is needed:
    % 1. Arrows which do not update the bounding box (which is most of them).
    % 2. Line caps/joins and mitres that extend outside the natural bounding 
    %    box of the path (these are not calculated by PGF).
    % 3. Other reasons that haven't been anticipated.
    fading xsep/.store in=\pgfpathfadingxsep,
    fading ysep/.store in=\pgfpathfadingysep,
    fading sep/.style={fading xsep=#1, fading ysep=#1},
    fading sep=0.0cm,
    shading path/.code={%
        % Prevent this stuff happning recursively.
        \iftikz@shading@path%
        \else%
        \tikz@shading@pathtrue%
        % \tikz@addmode installs the `modes' (e.g., fill, draw, shade) 
        % to be applied to the path. It isn't usualy for doing more
        % changes to the path's construction.
        \tikz@addmode{%
            \pgfgetpath\pgf@currentfadingpath%
            % Get the boudning box of the current path size including the fading sep
            \pgfextract@process\pgf@fadingpath@southwest{\pgfpointadd{\pgfqpoint{\pgf@pathminx}{\pgf@pathminy}}%
                {\pgfpoint{-\pgfpathfadingxsep}{-\pgfpathfadingysep}}}%%
            \pgfextract@process\pgf@fadingpath@northeast{\pgfpointadd{\pgfqpoint{\pgf@pathmaxx}{\pgf@pathmaxy}}%
                {\pgfpoint{\pgfpathfadingxsep}{\pgfpathfadingysep}}}%
            % Clear the path
            \pgfsetpath\pgfutil@empty%                          
            % Interrupt the path and picture to create a fading.
            \pgfinterruptpath%
            \pgfinterruptpicture%
            \begin{tikzfadingfrompicture}[name=.]
                \path [shade=none,fill=none, #1] \pgfextra{%
                    % Set the softpath. Any transformations in #1 will have no effect.
                    % This will *not* update the bounding box...
                    \pgfsetpath\pgf@currentfadingpath%
                    % ...so it is done manually.
                    \pgf@fadingpath@southwest
                    \expandafter\pgf@protocolsizes{\the\pgf@x}{\the\pgf@y}%
                    \pgf@fadingpath@northeast%
                    \expandafter\pgf@protocolsizes{\the\pgf@x}{\the\pgf@y}%
                };
                % Now get the bounding of the picture.
                \xdef\pgf@fadingboundingbox@southwest{\noexpand\pgfqpoint{\the\pgf@picminx}{\the\pgf@picminy}}%
                \xdef\pgf@fadingboundingbox@northeast{\noexpand\pgfqpoint{\the\pgf@picmaxx}{\the\pgf@picmaxy}}%
                %
            \end{tikzfadingfrompicture}%
            \endpgfinterruptpicture%
            \endpgfinterruptpath%
            % Install a rectangle that covers the shaded/faded path picture.                                
            \pgfpathrectanglecorners{\pgf@fadingboundingbox@southwest}{\pgf@fadingboundingbox@northeast}%
            % Make the fading happen.
            \def\tikz@path@fading{.}%
            \tikz@mode@fade@pathtrue%
            \tikz@fade@adjustfalse%10pt
            % Shift the fading to the mid point of the rectangle
            \pgfpointscale{0.5}{\pgfpointadd{\pgf@fadingboundingbox@southwest}{\pgf@fadingboundingbox@northeast}}%
            \edef\tikz@fade@transform{shift={(\the\pgf@x,\the\pgf@y)}}%
        }%
        \fi%
    }
}
\makeatother
%-------------------------------------------------------------------------------------
%https://tex.stackexchange.com/questions/197793/how-to-draw-gradient-arrows-with-tikz
\makeatletter
\def\createshadingfromlist#1#2#3{%
    \pgfutil@tempcnta=0\relax
    \pgfutil@for\pgf@tmp:={#3}\do{\advance\pgfutil@tempcnta by1}%
    \ifnum\pgfutil@tempcnta=1\relax%
    \edef\pgf@spec{color(0)=(#3);color(100)=(#3)}%
    \else%
    \pgfmathparse{50/(\pgfutil@tempcnta-1)}\let\pgf@step=\pgfmathresult%
    %
    \pgfutil@tempcntb=1\relax%
    \pgfutil@for\pgf@tmp:={#3}\do{%
        \ifnum\pgfutil@tempcntb=1\relax%
        \edef\pgf@spec{color(0)=(\pgf@tmp);color(25)=(\pgf@tmp)}%
        \else%
        \ifnum\pgfutil@tempcntb<\pgfutil@tempcnta\relax%
        \pgfmathparse{25+\pgf@step/4+(\pgfutil@tempcntb-1)*\pgf@step}%
        \edef\pgf@spec{\pgf@spec;color(\pgfmathresult)=(\pgf@tmp)}%
        \else%
        \edef\pgf@spec{\pgf@spec;color(75)=(\pgf@tmp);color(100)=(\pgf@tmp)}%
        \fi%
        \fi%
        \advance\pgfutil@tempcntb by1\relax%
    }%
    \fi%
    \csname pgfdeclare#2shading\endcsname{#1}{100}\pgf@spec%
}
\makeatother

\createshadingfromlist{shading1}{vertical}{red,yellow,green,cyan,blue}
\createshadingfromlist{shading2}{vertical}{red,green,yellow}
\createshadingfromlist{shading3}{vertical}{red,black,blue,green,cyan,orange,yellow}


\begin{document}

\begin{figure}[H]
\centering
\begin{tikzpicture}
  \begin{axis}[
  ticks=none,
  grid=none,
  xmin=0,xmax=100,
  ymin=0,ymax=100,
  axis lines = middle,
  set layers,
  xlabel={$t$},ylabel={$T$},
  x label style={at={(1,0)},right},
  y label style={at={(0,1)},above},
%  colormap={redblue}{rgb255(0cm)=(255,0,0); rgb255(1cm)=(0,0,255)}
               ]
    \path [shading=shading1, shading path={draw=transparent!0, ultra thick,}]
    (20,90) to[out=270,in=110] (25,60) to[out=335,in=115] (35,45) to[out=0,in=180] (70,45) to[out=305,in=150] (90,20);
%    \draw [ultra thick] (20,90) to[out=270,in=110] (25,60) to[out=335,in=115] (35,45) to[out=0,in=180] (70,45) to[out=305,in=150] (90,20);
    \node[inner sep=0pt, label={[outer sep=-2pt]45:A}] at (20,90) {} ;
    \node[label={[outer sep=-2pt]45:B}] at (25,60) {} ;
    \node[label={[outer sep=-2pt]45:C}] at (35,45) {} ;
    \node[label={[outer sep=-2pt]45:D}] at (70,45) {} ;
    \node[label={[outer sep=-2pt]45:E}] at (90,20) {} ;
    \addplot[only marks, mark options={solid,draw=green,fill=green}]
    coordinates {
    (20,90) (25,60) (35,45) (70,45) (90,20)
    };
    \end{axis}
\end{tikzpicture}
\end{figure}

\end{document}

Related Solutions

[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)

[Tex/LaTex] How to define the default vertical distance between nodes

I don't really get the question so I hope this is what you wanted. If you include a full document (such that we copy paste and see the problem on our systems) things are much more easier.

Here, you can change the default setting within a scope but your block style had a node distance which was resetting every time it is issued. I've made it 2mm such that we can see the difference easier.

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows,shapes.geometric,positioning}

\begin{document}
\begin{tikzpicture}[decision/.style={diamond, draw, text width=4.5em, text badly centered, node distance=3.5cm, inner sep=0pt},
                    block/.style   ={rectangle, draw, text width=6em, text centered, rounded corners, minimum height=4em, minimum height=2em},
                    cloud/.style   ={draw, ellipse, minimum height=2em},
                    line/.style    ={draw,-latex'},
                    node distance = 1cm, 
                    auto]
    \node [block] (1st) {1st};
    \node [block, right= of 1st]  (2nd1) {2nd1};
\begin{scope}[node distance=2mm and 10mm]%Here we change it for everything inside this scope
    \node [block, above= of 2nd1] (2nd2) {2nd2};
    \node [block, below= of 2nd1] (2nd3) {2nd3};
    \node [block, right= of 2nd1] (3rd1) {3rd1};
    \node [block, above= of 3rd1] (3rd2) {3rd2};
    \node [block, above= of 3rd2] (3rd3) {3rd3};
\end{scope}
    \node [block, below= of 3rd1] (3rd4) {3rd4};
    \node [block, below= of 3rd4] (3rd5) {3rd5};

    \path [line] (1st) -- (2nd1);
    \path [line] (2nd1) -- (2nd2);
    \path [line] (2nd1) -- (2nd3);
    \path [line] (2nd2) -- (3rd3);
    \path [line] (2nd1) -- (3rd1);
    \path [line] (1st) -- (2nd1);
\end{tikzpicture}
\end{document}

enter image description here