making an loss vs model complexity graph using tikz

Question

Since I am writing my thesis on machine learning, I wanted to illustrate some issues with this graph using tikz. Right now, I don't know how to do this since I'm a novice at using tikz. Anyone who can help me out? Thank you a lot!

Answer 1

To give you a start.

\documentclass[tikz,border=3mm]{standalone}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[thick,font=\sffamily,line cap=round,>=stealth,node
    distance=1em]
 \draw [<->] (0,5) node[below left]{Loss} |- (7,0) node[below left]{Model complexity};
 \draw (0.8,5) to[bend right=50] node[pos=0.7,above right] {Training loss}(6,0.8);
 \draw (1.2,5) to[out=-80,in=180] (3,3) to[out=0,in=-155]
  node[pos=0.2,below right] {Generalization loss} (6,4);
 \draw[loosely dotted] (3,0) -- (3,5) node[above] (P) {Optimum};
 \path node[base left=of P] (U) {Underfitting}
    node[base right=of P] (O) {Overfitting};
 \draw[->] ([yshift=1ex]U.north east) -- ([yshift=1ex]U.north west);
 \draw[->] ([yshift=1ex]O.north west) -- ([yshift=1ex]O.north east);    
\end{tikzpicture}
\end{document}