# pgfplots: read data, calculate diagram

I'm trying to create a diagram with pgfplots. I have some data, which I'd like to have stored in the diagram code, alternatively (preferably not) in a separate file.

What I need to do is to calculate the cumulative percentage of the data. In other words, each data point is calculated by summing each of the numbers in the y column from the previous lines, dividing them by the sum of all numbers in the y column, and multiply by 100. For example, data point 3 would be calculated by (0 + 435 + 111 + 51) / 646 * 100 = 92%. (646 is the sum of all numbers in the y column)

Below are the numbers, and the diagram I'd like to create from them.

%x  y
0   0
1   435
2   111
3   51
4   23
5   10
6   5
7   5
8   3
9   3


Thank you very much in advance!

You can use the pgfplotstable package that ships with PGFPlots to calculate the cumulative percentage:

\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\usepackage{filecontents}

\begin{filecontents*}{data.dat}
x  y
0   0
1   435
2   111
3   51
4   23
5   10
6   5
7   5
8   3
9   3
\end{filecontents*}

\begin{document}

% Read the data table into a macro

% Calculate the sum of the y column
\pgfmathsetmacro\pgfplotstablesum{0}
\pgfplotstableforeachcolumnelement{y}\of\datatable\as\yvalue{
\pgfmathsetmacro\pgfplotstablesum{\pgfplotstablesum+\yvalue}
}

% Define a "virtual column" that calculates the cumulative percentage on the fly
\pgfplotstableset{
create on use/cumulative percentage/.style={
create col/expr={\pgfmathaccuma + 100*\thisrow{y}/\pgfplotstablesum}
}
}

\begin{tikzpicture}
\begin{axis}[
enlargelimits=false,
axis lines*=left
]
\addplot [black, thick, mark=*] table [y=cumulative percentage] {\datatable} node {};
\end{axis}
\end{tikzpicture}
\end{document}