[Tex/LaTex] Plotting standard error

Question

I am trying to create a chart with the std error but I can't seem to get it to work the way I want it to. I want to get rid of the line between every entry. This is what I have right now:

\begin{tikzpicture} 
\begin{axis} \addplot+[error bars/.cd,y dir=both,y explicit]
    coordinates { (0,0) +- (0.5,2) (0.5,1) +- (0.4,0.2) (1,2) (2,5) +- (1,0.1) };
\end{axis} \end{tikzpicture}

This is what I want:

And I also wonder how you can read data form a .txt file and put it into the plot as well with x and y labels.

Data.txt:<br>

X Y Y_error
124 3.385995 0.866002
112 3.133745 0.937226
99 2.906316 0.895013
87 2.586054 0.835342
74 2.346789 0.792954
61 2.283117 0.699818
49 2.012212 0.909995
37 1.919941 1.366541
24 1.809623 1.691634
11 5.603446 13.825383

Answer 1

Since this is too long for a comment and I don't want to mess with @Jesse's answer - which obviously is the base for this - my take on what you're trying to achieve is:

Update: reversing the x axis is easily achieved with x dir=reverse.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\usepackage{filecontents}
\begin{filecontents*}{\jobname.dat}
124 3.385995 0.866002
112 3.133745 0.937226
99 2.906316 0.895013
87 2.586054 0.835342
74 2.346789 0.792954
61 2.283117 0.699818
49 2.012212 0.909995
37 1.919941 1.366541
24 1.809623 1.691634
11 5.603446 13.825383
\end{filecontents*}

\begin{document}
\begin{tikzpicture} 
\begin{axis}[x dir=reverse]
\addplot+[only marks, mark=o,error bars/.cd, y dir=both,y explicit]
 coordinates { 
(0,0)    +- (0.5,2) 
(0.5,1) +- (0.4,0.2) 
(1,2) 
(2,5)    +- (1,0.1) };
\end{axis} 
\end{tikzpicture}

\begin{tikzpicture}
\begin{axis}[x dir=reverse]
\addplot [color=blue, only marks,mark=o,]
 plot [error bars/.cd, y dir = both, y explicit]
 table[row sep=crcr, y error index=2]{\jobname.dat};
\end{axis}
\end{tikzpicture}%
\end{document}

As @Jesse noted, the magic lies in only marks,mark=o for suppressing the line, while plot [error bars/.cd, y dir = both, y explicit] sets what error bars are to be shown and y error index=2 specifies their position in the data table.