Hello Martin,
I believe there are two solutions:
1. You are explicitly assigning columns anyway. You could assign your
temporary intermediate solutions to global variables and dereferences
that one. This is a dirty hack, I agree.
2. You can safely use \pgfplotstablegetelem{ row }{ col }\of table
where row is an integer, 0<=row<number rows and col a column name. Note
that row currently has to be a constant (not an expression). You can use
\pgfplotstablegetrowsof{ file name or \loadedtable }
to retrieve the total number of rows for some table programmatically.
Some side-note: make sure that you terminate your code lines by '%' --
otherwise, TeX considers the newline character to be a whitespace and
produces spurious white space in your table (or shifts the table).
Here would be your code:
\documentclass{article}
\usepackage{tikz}
\usepackage{pgfplots}
\usepackage{pgfplotstable}
\pgfplotsset{compat=newest}
\usepackage{filecontents}
\begin{filecontents*}{testdata.table}
Val
2
1
3
\end{filecontents*}
\pgfplotstableread{testdata.table}{\testdata}
\pgfplotstablecreatecol[%
create col/assign/.code={%
\getthisrow{Val}\entry
\ifnum\pgfplotstablerow>0
\pgfmathsetmacro{\entry}{max(\entry,\pgfmathaccuma)}%
\fi
\edef\pgfmathaccuma{\entry}%<--- CF : ATTENTION: do not forget
'%' after lines otherwise TeX introduces spurious spaces
\xdef\MAXVAL{\pgfmathaccuma}%<-- CF: this is a "dirty hack":
simply write the result to some global variable - which can be used at
any place in the file.
\pgfkeyslet{/pgfplots/table/create col/next content}\entry
}]{Max}\testdata
\pgfplotstablecreatecol[%
create col/assign/.code={%
\getthisrow{Val}\entry
\ifnum\pgfplotstablerow>0
\pgfmathsetmacro{\entry}{min(\entry,\pgfmathaccuma)}%
\fi
\edef\pgfmathaccuma{\entry}
\pgfkeyslet{/pgfplots/table/create col/next content}\entry
}]{Min}\testdata
\pgfplotstablecreatecol[%
create col/assign/.code={%
\getthisrow{Val}\entry
\ifnum\pgfplotstablerow>0
\pgfmathsetmacro{\entry}{add(\entry,\pgfmathaccuma)}%
\fi
\edef\pgfmathaccuma{\entry}
\pgfkeyslet{/pgfplots/table/create col/next content}\entry
}]{Sum}\testdata
\pgfplotstablecreatecol[%
create col/assign/.code={%
\getthisrow{Sum}\entry
\pgfmathsetmacro{\entry}{divide(\entry,\pgfplotstablerows)}%
\pgfkeyslet{/pgfplots/table/create col/next content}\entry
}]{Avg}\testdata
\begin{document}
\pgfplotstabletypeset[%
every head row/.style={before row=\hline,after row=\hline},
every last row/.style={after row=\hline},
columns/Val/.style={fixed,fixed zerofill,precision=2},
columns/Min/.style={fixed,fixed zerofill,precision=2},
columns/Max/.style={fixed,fixed zerofill,precision=2},
columns/Avg/.style={fixed,fixed zerofill,precision=2},
columns/Sum/.style={fixed,fixed zerofill,precision=2},
]{\testdata}
% CF: dirty hack result: simply dereference global variable:
The max value is \pgfmathprintnumber{\MAXVAL}.
% CF: clean solution: get a single value of the table.
\pgfplotstablegetelem{2}{Avg}\of\testdata
The average value is \pgfmathprintnumber{\pgfplotsretval}.
% CF: get number of rows, subtract by 1, and use that value:
{%
\pgfplotstablegetrowsof{\testdata}%
\count0=\pgfplotsretval % means: store \pgfplotsretval into artihmetic
TeX register
\advance\count0 by-1 % subtract 1 from that register
\edef\pgfplotsretval{\the\count0}% store result into \pgfplotsretval (as
string)
\pgfplotstablegetelem{\pgfplotsretval}{Sum}\of\testdata
The sum is \pgfmathprintnumber{\pgfplotsretval}.
}% this here restores \count0 to its previous value
\end{document}
Best regards
Christian
Am 23.03.2012 12:37, schrieb Martin Heller:
> I would like to perform some simple calculations on columns of data that
> I am importing from external files, typesetting with pgfplotstable, and
> plotting with pgfplots.
>
> I can do the calculations using \pgfplotstablecreatecol but I can't
> figure out how to report the result without typesetting the entire
> column of intermediate calculations. In the example below I would like
> to find the maximum, minimum, sum and average of the data in the Val
> column and be able to use the results outside the table. In the example
> the results are in the final row of the corresponding columns.
>
> Can I typeset the results outside the table with the tools provided by
> pgfplots/pgfplotstable or are there an easier/better way to perform such
> calculations once the data has been read with \pgfplotstableread?
>
> \documentclass{article}
> \usepackage{tikz}
> \usepackage{pgfplots}
> \usepackage{pgfplotstable}
> \pgfplotsset{compat=newest}
> \usepackage{filecontents}
>
> \begin{filecontents*}{testdata.table}
> Val
> 2
> 1
> 3
> \end{filecontents*}
>
> \pgfplotstableread{testdata.table}{\testdata}
> \pgfplotstablecreatecol[%
> create col/assign/.code={%
> \getthisrow{Val}\entry
> \ifnum\pgfplotstablerow>0
> \pgfmathsetmacro{\entry}{max(\entry,\pgfmathaccuma)}%
> \fi
> \edef\pgfmathaccuma{\entry}
> \pgfkeyslet{/pgfplots/table/create col/next content}\entry
> }]{Max}\testdata
>
> \pgfplotstablecreatecol[%
> create col/assign/.code={%
> \getthisrow{Val}\entry
> \ifnum\pgfplotstablerow>0
> \pgfmathsetmacro{\entry}{min(\entry,\pgfmathaccuma)}%
> \fi
> \edef\pgfmathaccuma{\entry}
> \pgfkeyslet{/pgfplots/table/create col/next content}\entry
> }]{Min}\testdata
>
> \pgfplotstablecreatecol[%
> create col/assign/.code={%
> \getthisrow{Val}\entry
> \ifnum\pgfplotstablerow>0
> \pgfmathsetmacro{\entry}{add(\entry,\pgfmathaccuma)}%
> \fi
> \edef\pgfmathaccuma{\entry}
> \pgfkeyslet{/pgfplots/table/create col/next content}\entry
> }]{Sum}\testdata
>
> \pgfplotstablecreatecol[%
> create col/assign/.code={%
> \getthisrow{Sum}\entry
> \pgfmathsetmacro{\entry}{divide(\entry,\pgfplotstablerows)}%
> \pgfkeyslet{/pgfplots/table/create col/next content}\entry
> }]{Avg}\testdata
>
> \begin{document}
>
> \pgfplotstabletypeset[%
> every head row/.style={before row=\hline,after row=\hline},
> every last row/.style={after row=\hline},
> columns/Val/.style={fixed,fixed zerofill,precision=2},
> columns/Min/.style={fixed,fixed zerofill,precision=2},
> columns/Max/.style={fixed,fixed zerofill,precision=2},
> columns/Avg/.style={fixed,fixed zerofill,precision=2},
> columns/Sum/.style={fixed,fixed zerofill,precision=2},
> ]{\testdata}
>
> \end{document}
>
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