I'm facing problems with my plots again.
The first one is that the produced plot is not centered in the pdf.
See here: 
For plots, like the one as example I use
\includegraphics[trim= 20mm 140mm 0mm 45mm,width....
to get it centered in my document. But I have to figure out the patterns for every plot because they vary in size (height and width). So is there a simple way to do this? As seen in the code I set the size to:
width=15cm,
height=9cm,
and want to keep it that way.
Second problem (probably way to easy) is the size of my legend.
It should be font=\large or font=\Large. Well, this kind code does not
work in a legend with \LegendImage \LegendEntry...or does it?
Thanks in advance!
Here comes the code:
\begin{filecontents*}{data.txt}
c b
9 3.5e-07
8 3.5e-05
7 3.5e-03
6 60
5 8000
4 10000
3 12000
2 140000
1 160000
0 1800000
\end{filecontents*}
\documentclass[paper=a4,ngerman,xcolor=dvipsnames]{article}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{pgfplots}
\pgfplotsset{compat=1.14}
\usetikzlibrary{positioning}
\usepackage{siunitx}
\newcommand\LegendImage[1]{% from pgfplots.code.tex
\draw[%
/pgfplots/mesh=false,%
bar width=3pt,%
bar shift=0pt,%
%
mark repeat=2,%
mark phase=2,#1]
plot coordinates {
(0cm,0cm)
(0.3cm,0cm)
(0.6cm,0cm)%
};
}
\newcommand\LegendEntry[1]{\node[anchor=west,black,font=\footnotesize,inner xsep=2pt]{#1};}
\def\showmark#1{\tikz\node[red!95!black]{\pgfuseplotmark{#1}};}
\newcommand{\RM}[1]{\MakeUppercase{\romannumeral #1{.}}}
\begin{document}
\pagenumbering{gobble}
\begin{center}
\begin{tikzpicture}[trim axis left, trim axis right]
\begin{semilogxaxis}[
grid=both,
width=15cm,
height=9cm,
% axis equal,
xtick pos=left, style={font=\Large},
ytick pos=left, style={font=\Large},
label style={font=\Large},
title style={draw,fill=none,name=legend},
title={%
\showmark{pentagon*}=$\SI{100}{\kilo\Hz}$,
\showmark{triangle*}=$\SI{10}{\kilo\Hz}$,
\showmark{square*}=$\SI{1}{\kilo\Hz}$,
\showmark{diamond*}=$\SI{100}{\Hz}$,
\showmark{10-pointed star}=$\SI{10}{\Hz}$,
\showmark{oplus}=$\SI{1}{\Hz}$,
\showmark{o}=$\SI{20}{\mHz}$},
xlabel={F}, ylabel={Y},
scatter,
point meta=explicit symbolic,
scatter/classes={
x={},
g={mark=pentagon*,red!95!black},
f={mark=triangle*,red!95!black},
e={mark=square*,red!95!black},
d={mark=diamond*,red!95!black},
c={mark=10-pointed star,red!95!black},
b={mark=oplus,red!95!black},
a={mark=o,red!95!black},
z={mark=*,red!80!black}
},
]
\node[font=\large] at (1800000,6.5) {\RM{1}};
\node[font=\large] at (140000,6.5) {\RM{2}};
\node[font=\large] at (60,6.5) {\RM{3}};
\node[font=\large] at (3.5e-05,6.5) {\RM{4}};
\node[font=\large] at (3.5e-06,6.5) {\RM{5}};
\addplot [blue!99!green,mark=+] table [x=b,y=c] {data.txt};
\addplot[mark=none, black] coordinates {(1800000,0) (1800000,6)};
\addplot[mark=none, black] coordinates {(140000,0) (140000,6)};
\addplot[mark=none, black] coordinates {(60,0) (60,6)};
\addplot[mark=none, black] coordinates {(3.5e-05,0) (3.5e-05,6)};
% coordinate for upper left corner of legend
\coordinate (legpos) at (rel axis cs:0.02,0.98);
\end{semilogxaxis}
\matrix (m) at (legpos) [
fill=white,
draw=black,
anchor=north west,
cells={anchor=west}]
{
\LegendImage{color=black!70!green,mark=x,mark size=2pt} & \LegendEntry{$\SI{2}{\milli \ampere}$}; \\
\LegendImage{color=blue!99!green,mark=x,mark size=2pt} & \LegendEntry{$\SI{5}{\milli \ampere}$}; \\
};
\end{tikzpicture}
\end{center}
\end{document}
font=\footnotesizepresent in the\LegendEntrymacro, not sure if you've noticed that. If you want a larger font, just edit that. For the centering, if reducing the width of the plot is not an option, see http://tex.stackexchange.com/questions/39435 or http://tex.stackexchange.com/questions/16582 – Torbjørn T. Mar 21 '17 at 19:09.logfile:LaTeX Warning: Unused global option(s): [paper=a4,xcolor=dvipsnames].For the standardarticleclass, usea4paperto set the papersize, notpaper=a4. And use justdvipsnames, notxcolor=dvipsnames. – Torbjørn T. Mar 21 '17 at 19:12