\begin{tikzpicture}
\begin{semilogyaxis}[
ymin=0.02,
ytick={0.0416,0.2083,1,4,14,56},
yticklabels={1 hr,5 hrs,1 day,4 days,2 wks,8 wks},
grid=major,
xtick={27,53,79},
xticklabels={,,},
log basis y=2,
log ticks with fixed point,
only marks,
xticklabels={,,},
title={Problems (in order of appearance)},
xlabel={},
ylabel=Time until solved (octiles),
enlargelimits=false]
\addplot[color=black, mark=*, mark size=1pt] table[x=problem,y=1] {octiles.txt}; 
\addplot[color=red, mark=*, mark size=1.5pt] table[x=problem,y=2] {octiles.txt}; 
\addplot[color=black, mark=*, mark size=1pt] table[x=problem,y=3] {octiles.txt}; 
\addplot[color=blue, mark=*] table[x=problem,y=4] {octiles.txt}; 
\addplot[color=black, mark=*, mark size=1pt] table[x=problem,y=5] {octiles.txt}; 
\addplot[color=red, mark=*, mark size=1.5pt] table[x=problem,y=6] {octiles.txt}; 
\addplot[color=black, mark=*, mark size=1pt] table[x=problem,y=7] {octiles.txt}; 
\end{semilogyaxis}
\end{tikzpicture}
