# Problem of superimpose and how to change legend symbol

Given the plot as follows

I have two problems:

1. a and b are superimposed on each other, how should I make this clear on the graph?
2. How could I change legend c to other icons like star? (It looks a bit similar to a)

The code is shown below:

\documentclass[tikz]{standalone}
\usepackage{pgf}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{arrows,automata,positioning}
\begin{document}
\begin{tikzpicture}[font=\sffamily]
\begin{semilogyaxis}[title=Random Dataset,
legend pos=outer north east,
legend style={draw=none},
xtick={1,2,...,9},
scaled ticks=false,
log ticks with fixed point={1000 sep=},
axis x line=bottom,
axis y line=left,
axis line style=-,
minor tick style={draw=none},
enlargelimits,
ylabel = Solving Time (ms),
xlabel = Number of Constraints,
every axis legend/.append style={xshift=-10pt}
]
\legend{a,b,c}
\end{semilogyaxis}
\end{tikzpicture}
\end{document}

-

One way would be to change the plot styles so that both the a and b markers could be seen. For example using a howllow square for b allows the a points to be visible.

For your second question, using \addplot+[mark=triangle] uses a triangle shape which is sufficiently different so that it won't be confused with the other markers.

## Code:

\documentclass[tikz]{standalone}
\usepackage{pgf}
\usepackage{graphicx}
\usepackage{tikz}
\usepackage{pgfplots}
\usetikzlibrary{arrows,automata,positioning}
\begin{document}
\begin{tikzpicture}[font=\sffamily]
\begin{semilogyaxis}[title=Random Dataset,
legend pos=outer north east,
legend style={draw=none},
xtick={1,2,...,9},
scaled ticks=false,
log ticks with fixed point={1000 sep=},
axis x line=bottom,
axis y line=left,
axis line style=-,
minor tick style={draw=none},
enlargelimits,
ylabel = Solving Time (ms),
xlabel = Number of Constraints,
every axis legend/.append style={xshift=-10pt}
]