% This file is embedded in datatool-user.pdf version 3.0.1 2025-03-05
% Example 93 Loops and Alignment
% Label: "ex:constructtab"
% arara: pdflatex
% arara: pdfcrop
\documentclass[12pt]{article}
\pagestyle{empty}
% sample CSV file:
\begin{filecontents}[noheader,overwrite]{studentmarks.csv}
Surname,Forename,StudentNo,Assign1,Assign2,Assign3
"Smith, Jr",John,102689,68,57,72
"Brown",Jane,102647,75,84,80
"Brown",Jane,102646,64,92,79
"Brown",Andy,103569,42,52,54
"Adams",Zoë,105987,52,48,57
"Brady",Roger,106872,68,60,62
"Verdon",Clare,104356,45,50,48
\end{filecontents}

\usepackage{colortbl}
\usepackage{datatool} 

% Load data from studentmarks.csv file:
\DTLsetup{store-datum,default-name=marks}
\DTLread{studentmarks.csv}
% Commands to construct the tabular content:
\ExplSyntaxOn
% define variables:
\int_new:N \l_my_row_int
\tl_new:N \l_my_content_tl
\tl_new:N \l_my_forename_tl
\tl_new:N \l_my_surname_tl
\tl_new:N \l_my_mean_tl
% command to initialise:
\cs_new:Nn \my_init_content: 
{
 \tl_set:Nn \l_my_content_tl { \begin{tabular} { lr } }
 \int_zero:N \l_my_row_int
}
% command to finish off:
\cs_new:Nn \my_finish_content: 
 {
  \tl_put_right:Nn \l_my_content_tl { \end{tabular} }
 }
% command to append a row:
\cs_new:Nn \my_add_row:nn 
{
 \fp_compare:nNnF { #2 } < { 50 } 
 { \int_if_zero:nF { \l_my_row_int }
 {
  \tl_put_right:Nn \l_my_content_tl { \\ }
  }
  \int_incr:N \l_my_row_int
  \fp_compare:nNnT { #2 } > { 70 } 
  {
  \tl_put_right:Nn \l_my_content_tl { \rowcolor { yellow } }
  }
  \tl_put_right:Nx \l_my_content_tl { #1 & #2 }
  }
}
% define document command:
\NewDocumentCommand { \meanscorestab } { } 
{
% construct tabular:
 \my_init_content:
% iterate over the default database:
 \DTLmapdata
 {
% get the surname and forename for the current row:
  \DTLmapgetvalues
  {
  \l_my_surname_tl = Surname ,
  \l_my_forename_tl = Forename
  }
% calculate the mean:
   \DTLaction
  [
  keys={Assign1-},
  datum={round=1},
  return={ \l_my_mean_tl = mean },
  options=mean
  ]
  {row ~ aggregate}
  \my_add_row:nn
  { \l_my_forename_tl \c_space_tl \l_my_surname_tl }
  { \l_my_mean_tl }
  }
% finish construction:
 \my_finish_content: % expand the content:
 \l_my_content_tl }
\ExplSyntaxOff 
\begin{document}
\meanscorestab 
\end{document}