I am trying to plot a function that is the sum of another function based on the parameter.
A famous example of this is the "sum of squares", however the functions I really want to do this do not have an explicit formula.
The following example shows the result I would like to get and a method how I would like to have it, which is obviously not giving the correct result.
\documentclass[border=10]{standalone}\usepackage{tikz}\usepackage{pgfplots}\pgfplotsset{compat=1.9}\begin{document} % Explicit formula \pgfmathdeclarefunction{explicit_sum}{1}{% \pgfmathparse{(#1*(#1-1))/2}% } % The inner function \pgfmathdeclarefunction{square}{1}{% \pgfmathparse{#1*#1}% } % Compute the sum of another function % Does not work... \pgfmathdeclarefunction{manual_sum}{1}{% %Parameter should be integral \pgfmathtruncatemacro\cnt{#1} \pgfmathsetmacro\ret{0} \foreach \i in {1,...,\cnt} { \pgfmathsetmacro\ret{\ret + sum(\i)} } \pgfmathparse{\ret} } \begin{tikzpicture} \begin{axis} % Expected \addplot[samples at={1,...,10}] {explicit_sum(x)}; % Does not work \addplot[samples at={1,...,10}] {manual_sum(x)}; \end{axis} \end{tikzpicture}\end{document}