\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\usepackage{filecontents}
\usepackage{indentfirst}
\usepackage{amsmath}
\usepackage{float}
\usepackage{hhline}
\usepackage{multirow}
\usepackage{datatool}
\begin{filecontents}{data.dat}
28.7 28.4 43.4
0.2416 0.2415 nan
0.2420 0.2416 nan
0.2421 0.2416 nan
0.2416 0.2422 nan
0.2410 0.2422 nan
35.9 35.6 50.4
0.2695 0.2691 nan
0.2679 0.2691 nan
0.2691 0.2697 nan
0.2691 0.2691 nan
0.2686 0.2694 nan
42.6 42.3 57.4
0.2951 0.2953 nan
0.2950 0.2951 nan
0.2952 0.2956 nan
0.2951 0.2957 nan
0.2951 0.2954 nan
47.2 46.9 61.9
0.3091 0.3104 nan
0.3095 0.3107 nan
0.3106 0.3107 nan
0.3105 0.3110 nan
0.3107 0.3103 nan
51.3 51.1 66.1
0.3234 0.3231 nan
0.3231 0.3235 nan
0.3238 0.3233 nan
0.3229 0.3241 nan
0.3243 0.3230 nan
57.4 57.2 72.3
0.3417 0.3431 nan
0.3426 0.3431 nan
0.3422 0.3437 nan
0.3430 0.3427 nan
0.3429 0.3437 nan
\end{filecontents}
\pgfplotsset{compat=1.14}
\pgfplotstableread{data.dat}\Data
\begin{document}
\begin{table}
\title{Pendulum Data for Steel Ball}
\begin{tabular}{|l|l|l|l|} \hline
$d$ (cm) & $y$ (cm) & $\tau$ (s) & $\tau^2$ (s) \\\hhline{|=|=|=|=|}
\foreach \row in {0,...,35}
{
\newcount\countuno
\countuno=\row
\divide\countuno by 6
\multiply\countuno by 6
\ifnum\countuno=\row
\pgfplotstablegetelem{\row}{2}\of\Data \pgfmathsetmacro\dval{\pgfplotsretval}
\pgfplotstablegetelem{\row}{0}\of\Data \pgfmathsetmacro\yval{\pgfplotsretval}
\multirow{5}{*}{$\pgfmathprintnumber{\dval}$} & \multirow{5}{*}{$\pgfmathprintnumber{\yval}$}
\else
\pgfplotstablegetelem{\row}{0}\of\Data \pgfmathsetmacro\tval{\pgfplotsretval}
\pgfmathsetmacro\tsqrval{\tval ^ 2}
\advance\countuno by 1
\ifnum\countuno<\row
&
\fi
& $\pgfmathprintnumber{\tval}$ & $\pgfmathprintnumber{\tsqrval}$ \\\hline
\fi
}
\end{tabular}
\end{table}
\end{document}
me sale el error
! Missing \endgroup inserted.
<inserted text>
\endgroup
l.83 }
No veo donde podría estar el error. He pasado algún tiempo jugueteando con la sintaxis de las declaraciones if pero no parecen estar causando el problema y, hasta donde yo sé, el bucle foreach también se ve bien. Posiblemente tenga algo que ver con los comandos pgf. Sería realmente fantástico si alguien detectara el problema.
Respuesta1
No puedes iniciar el ciclo en una celda y terminarlo en otra.
Una solución alternativa es crear la tabla en la primera celda y entregarla toda a la vez.
Como estoy en contra \multirowde las tablas encarceladas, así es como puedes hacerlo booktabs.
\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\usepackage{filecontents}
\usepackage{amsmath}
\usepackage{booktabs}
\begin{filecontents}{\jobname.dat}
28.7 28.4 43.4
0.2416 0.2415 nan
0.2420 0.2416 nan
0.2421 0.2416 nan
0.2416 0.2422 nan
0.2410 0.2422 nan
35.9 35.6 50.4
0.2695 0.2691 nan
0.2679 0.2691 nan
0.2691 0.2697 nan
0.2691 0.2691 nan
0.2686 0.2694 nan
42.6 42.3 57.4
0.2951 0.2953 nan
0.2950 0.2951 nan
0.2952 0.2956 nan
0.2951 0.2957 nan
0.2951 0.2954 nan
47.2 46.9 61.9
0.3091 0.3104 nan
0.3095 0.3107 nan
0.3106 0.3107 nan
0.3105 0.3110 nan
0.3107 0.3103 nan
51.3 51.1 66.1
0.3234 0.3231 nan
0.3231 0.3235 nan
0.3238 0.3233 nan
0.3229 0.3241 nan
0.3243 0.3230 nan
57.4 57.2 72.3
0.3417 0.3431 nan
0.3426 0.3431 nan
0.3422 0.3437 nan
0.3430 0.3427 nan
0.3429 0.3437 nan
\end{filecontents}
\pgfplotsset{compat=1.14}
\pgfplotstableread{\jobname.dat}\Data
\newcount\countuno
\begin{document}
\begin{table}
\title{Pendulum Data for Steel Ball}
\begin{tabular}{llll}
\toprule
$d$ (cm) & $y$ (cm) & $\tau$ (s) & $\tau^2$ (s) \\
\midrule
\gdef\tablecontents{}%
\foreach \row in {0,...,35}
{%
\countuno=\row
\divide\countuno by 6
\multiply\countuno by 6
\ifnum\countuno=\row
\pgfplotstablegetelem{\row}{2}\of\Data
\pgfmathsetmacro\dval{\pgfplotsretval}%
\pgfplotstablegetelem{\row}{0}\of\Data
\pgfmathsetmacro\yval{\pgfplotsretval}%
\xdef\tablecontents{%
\unexpanded\expandafter{\tablecontents}%
\ifnum\row>0 \noexpand\midrule \fi
$\noexpand\pgfmathprintnumber{\dval}$ &
$\noexpand\pgfmathprintnumber{\yval}$
}%
\else
\pgfplotstablegetelem{\row}{0}\of\Data
\pgfmathsetmacro\tval{\pgfplotsretval}%
\pgfmathsetmacro\tsqrval{\tval ^ 2}%
\advance\countuno by 1
\xdef\tablecontents{%
\unexpanded\expandafter{\tablecontents}
\ifnum\countuno<\row &\fi
& $\noexpand\pgfmathprintnumber{\tval}$
& $\noexpand\pgfmathprintnumber{\tsqrval}$
\noexpand\\
}%
\fi
}%
\tablecontents
\bottomrule
\end{tabular}
\end{table}
\end{document}
