# What is the increment step of \fnpnodes?

Case 0 uses \fnpnodes and case 1 uses \curvepnodes to create nodes based on the given function(s).

\def\method#1{%
\ifcase#1
\fnpnodes[plotpoints=8]{1}{8}{\f[x]}{P}
\psxTick(/dx \pst@number\pst@dimb\space def dx 4 mul 1 add){x_j}
\or
\curvepnodes[plotpoints=8]{1}{8}{t|\f[t]}{P}
\psxTick(dt 4 mul 1 add){x_j}
\fi}


I have known that dt is the increment step of \curvepnodes. Now I am looking for the increment step of \fnpnodes. I tried using /dx \pst@number\pst@dimb\space def dx but it does not seem to work.

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot,pst-node}
\psset
{
algebraic,
ticks=none,
labels=none,
plotpoints=100,
}

\def\f[#1]{sin(3*#1)/2+#1/3+1}

\makeatletter
\def\method#1{%
\ifcase#1
\fnpnodes[plotpoints=8]{1}{8}{\f[x]}{P}
\psxTick(/dx \pst@number\pst@dimb\space def dx 4 mul 1 add){x_j}
\or
\curvepnodes[plotpoints=8]{1}{8}{t|\f[t]}{P}
\psxTick(dt 4 mul 1 add){x_j}
\fi}
\makeatother

\begin{document}

\begin{psgraph}(0,0)(-.5,-.5)(9.5,5){12cm}{!}
\method{1} % \method{0} does not work!
\multido{\iL=0+1,\iR=1+1}{\Pnodecount}{\pspolygon[fillstyle=solid,fillcolor=cyan!15](P\iL|0,0)(P\iL)(P\iR)(P\iR|0,0)}
\psplot[linecolor=cyan!75!blue]{0}{9}{\f[x]}
%\psxTick(N-P4.x){x_j} recommended
\end{psgraph}

\end{document}


What is the increment step of \fnpnodes?

\fnpnodes doesn't define an increment step on Postscript level, but the calculations are done on TeX-level. So you must do the calculations yourself with (x1 - x0)/(plotpoints - 1) if you need the step:
\fnpnodes[plotpoints=8]{1}{8}{\f[x]}{P}