[Tex/LaTex] Labels with arrows for an equation

beamertikz-arrowstikz-pgf

I am trying to adapt the second solution of "Label variables of the equation using Tikz without using itemize
" to my equation, P_t= P_T G_T G_t H_f.

The code is the following:

\documentclass{beamer}
\usetheme[progressbar=frametitle]{metropolis}
\setbeamertemplate{frame numbering}[fraction]
\useoutertheme{metropolis}
\useinnertheme{metropolis}
\usefonttheme{metropolis}
\usecolortheme{spruce}
\setbeamercolor{background canvas}{bg=white}
\definecolor{mygreen}{rgb}{.125,.5,.25}
\usecolortheme[named=mygreen]{structure}
\setbeamercovered{transparent=15}
\usepackage{pgfplots}
\usepackage{tikz}
\usetikzlibrary{positioning}
\tikzset{>=stealth}
\newcommand{\tikzmark}[3][]{\tikz[overlay,remember picture,baseline] \node [anchor=base,#1](#2) {#3};}
\begin{document}
\begin{frame}[t]{Channel model}
        \begin{itemize}
            \item<1-> The power coupled into the IC, $P_t$ is
        \end{itemize}
            \begin{equation*}
                P_t = \tikzmark{identity}{P_T} \tikzmark[red]{G}{G_T}\, 
                \tikzmark[blue]{L}{G_t} \tikzmark[purple]{C}{H_f}
            \end{equation*}

            \begin{tikzpicture}[overlay, remember picture,node distance =1.5cm]
                \node (identitydescr) [below left=of identity ]{transmitted power of the sender};
                \draw[,->,thick] (identitydescr) to [in=-90,out=90] (identity);
                \node[red] (Gdescr) [below =of G]{gain of the transmitter antenna};
                \draw[red,->,thick] (Gdescr) to [in=-90,out=90] (G);
                \node[blue,xshift=1cm] (Ldescr) [above right =of L]{gain of the box antenna};
                \draw[blue,->,thick] (Ldescr) to [in=45,out=-90] (L.north);
                \node[purple] (Cdescr) [below right =of C]{attenuation of the transmitted power};
                \draw[purple,->,thick] (Cdescr) to [in=-90,out=90] (C.south);
            \end{tikzpicture}
    \end{frame}
\end{document}

But it does not work as the linked solution above does. There seem to be several problems in the code, like tikzmark does not work with math like G_T. Besides, the labels can not break in several lines. I have tried \\but it does not work.
I would also like to be able to place the tikzpicture in some part below the text. Now it overlies the first text line, or if I put the tikzpicture into the itemize environment, the arrows and labels appear displaced.

I would like to know how to control the bend and position of the arrows specified with the in and out angles.

Regards

Best Answer

There are a couple of problems:

  • If you want to use things like P_T in the \tikzmark, you need math mode

  • Your previous definition of \tikzmark contained overlay as option, this hides the width of the content, thus all your letters were superimposed.

  • To get line breaks in your descriptions, you can use pass the text width option to the node.

  • if you load the metropolis theme, there is no need to load its outer, inner and font themes a second time.

And please don't listen to @marmot and accept his answer :)

\documentclass{beamer}

\usetheme[progressbar=frametitle]{metropolis}
\setbeamertemplate{frame numbering}[fraction]
\usecolortheme{spruce}
\setbeamercolor{background canvas}{bg=white}
\definecolor{mygreen}{rgb}{.125,.5,.25}
\usecolortheme[named=mygreen]{structure}
\setbeamercovered{transparent=15}
\usepackage{pgfplots}


\usepackage{amsmath} % loaded automatically by beamer
\usepackage{tikz}
\usetikzlibrary{positioning}
\tikzset{>=stealth}

\newcommand{\tikzmark}[3][]{\tikz[remember picture,baseline] \node [anchor=base,#1](#2) {$#3$};}

\begin{document}
\begin{frame}[t]{Channel model}
    \begin{itemize}
        \item<1-> The power coupled into the IC, $P_t$ is
    \end{itemize}
        \begin{equation*}
            P_t = \tikzmark{identity}{P_T}\tikzmark[red]{G}{G_T}
            \tikzmark[blue]{L}{G_t}\tikzmark[purple]{C}{H_f}
        \end{equation*}
       \begin{tikzpicture}[overlay, remember picture,node distance =1.5cm]
            \node[,text width=2cm] (identitydescr) [below left=of identity ]{transmitted power of the sender};
            \draw[,->,thick] (identitydescr) to [in=-90,out=90] (identity);
            \node[red,text width=2cm] (Gdescr) [below =of G]{gain of the transmitter antenna};
            \draw[red,->,thick] (Gdescr) to [in=-90,out=90] (G);
            \node[blue,xshift=1cm,text width=2cm] (Ldescr) [above right =of L]{gain of the box antenna};
            \draw[blue,->,thick] (Ldescr) to [in=45,out=-90] (L.north);
            \node[purple,text width=2cm] (Cdescr) [below right =of C]{attenuation of the transmitted power};
            \draw[purple,->,thick] (Cdescr) to [in=-90,out=90] (C.south);
        \end{tikzpicture}
\end{frame}
\end{document}

enter image description here

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