I have used `\pgfplotstableset` to assign column names in the preamble. However, I don't know how to access them.

```
\documentclass{article}
\usepackage{amsmath}
\usepackage{pgfplots, pgfplotstable, filecontents}
\pgfplotsset{compat=1.6}

\begin{filecontents}{test.dat}
  Time Distance
   0 0 
   1 1 
   3 2 
\end{filecontents}

\pgfplotstableset{
   columns/Time/.style={
     column name={$t_{\alpha}$},
   },
   columns/Distance/.style={
      column name={$D_{\alpha}$},
   },
}

\begin{document}
  \pgfplotstableread{test.dat}\loadedtable

  \pgfplotstabletypeset{\loadedtable}

  \pgfplotstableforeachcolumn\loadedtable\as\col{%
     column name is ‘\col’; index is \pgfplotstablecol;\par
  }
\end{document}

```

The column names are modified correctly in the table but when I try to access them using `\col` I don't get the modified names. What is the key for column names? 

As `pgfplots` does not support mathmode expressions in the column names, I am planning to use `\pgfplotstableset` in the preamble to create a document wide list of column names and then use it for legends in the figures throughout the document.

**Edit:** I also tried

```
\foreach \y in {0,1}{
  \pgfplotstablegetcolumnnamebyindex{\y}\of{\loadedtable}\to{\colname}
  \colname
}

```

to get the column names. But with the same result. Also, `\pgfplotstablegetcolumnnamebyindex` is not mentioned in the manual for `pgfplotstable` v1.6. I got it from another post here.

**Edit2:** Further exploration of the issue. Consider the following code and the output of the latex file.

```
\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz,pgfplots,pgfplotstable,filecontents}
\pgfplotsset{compat=1.6}
\begin{filecontents}{test1.dat}
  Time Distance
  1 1
\end{filecontents}

\begin{filecontents}{test2.dat}
  Time Velocity
  2 3
\end{filecontents}

\begin{document}
\pgfplotstableread{test1.dat}\tableone \pgfplotstableread{test2.dat}\tabletwo

\noindent \pgfplotstabletypeset{\tableone}\\
\pgfplotstabletypeset{\tabletwo}\newline\line(1,0){80}

\pgfplotstableset{
   columns/Time/.style={
     column name={$t_{\alpha}$},
   }
}    

\noindent \pgfplotstabletypeset{\tableone}\\
\pgfplotstabletypeset{\tabletwo}\newline\line(1,0){80}

\pgfkeyssetvalue{/pgfplots/table/column name}{$t_{\beta}$}

\noindent \pgfplotstabletypeset{\tableone}\\
\pgfplotstabletypeset{\tabletwo}\newline\line(1,0){80}

\pgfkeysvalueof{/pgfplots/table/column name}
\end{document}

```

Output is:
![enter image description here](https://i.stack.imgur.com/N9qKG.png)

So here I show that `\pgfplotstableset` is indeed useful. Once an association has been made between a column header (as read from the input file) and the column name that one wants displayed it will be useful across multiple tables. As pointed out by @percusse and as mentioned in the `\pgfplotstable` manual, this function cannot be used as the scope of the definition is limited to `\pgfplotstabletypeset`.

I hope to use `\pgfkeys` instead. After going through `pgfplotstable.code.tex` to see the implementation of `column name` key, I tried to (unsuccessfully) use `\pgfkeys`. I am new to the `\pgfkeys` and hence I was not able to figure out how to access individual column names. 

Waiting for new ideas.