This is an expansion of the problem I posted, which @John Kormylo has provided a solution for.
https://tex.stackexchange.com/questions/640726/create-custom-tags-for-questions-in-exam-class
Here is worked solution from John.
\documentclass[addpoints]{exam}
\usepackage{tikz}% foreach and pgfmath
\newcommand{\tag}[1]{\expandafter\gdef\csname tagofq@\roman{question}\endcsname{#1}}
\makeatletter
\newcommand{\taglist}[1]{% #1 = comma delimmited list of tags (in order) for summary
\@ifundefined{exam@numquestions}{}{%
\bgroup% use local definitions
\lineskip=0pt
\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut Tag}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut Question}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut Points}}\newline
\foreach \x in {#1} {\count1=0
\let\qlist=\empty
\edef\pointsum{0}%
\loop\ifnum\count1<\exam@numquestions\relax
\advance\count1 by 1
\@ifundefined{tagofq@\@roman\count1}{}{%
\edef\thistag{\csname tagofq@\@roman\count1\endcsname}%
\ifx\x\thistag\relax
\ifx\empty\qlist\relax
\edef\qlist{\the\count1}%
\else
\edef\qlist{\qlist, \the\count1}%
\fi
\edef\thispoints{\csname pointsofq@\@roman\count1\endcsname}%
\pgfmathparse{int(\pointsum+\thispoints)}%
\let\pointsum=\pgfmathresult
\fi}%
\repeat
\vskip-\fboxrule\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut\x}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\qlist}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\pointsum}}\newline}%
\vskip-\fboxrule\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut Total}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\exam@numpoints}}
\egroup}}
\makeatother
\begin{document}
\begin{questions}
\question[1] \tag{Algebra}
This is Question 1. This is tagged against Algebra.
\question[2] \tag{Equations}
This is Question 2.This is tagged against Equations.
\question[2] \tag{Data}
This is Question 3.This is tagged against Data.
\question[1] \tag{Algebra}
This is Question 4. This is tagged against Algebra.
\question[2] \tag{Algebra}
This is Question 5.This is tagged against Algebra.
\question[2] \tag{Data}
This is Question 6.This is tagged against Data.
\end{questions}
\taglist{Algebra,Data,Equations}
\end{document}
I would like to modify John's code to include \parts.
Here is a sample .tex file.
\documentclass[addpoints]{exam}
\begin{document}
\begin{questions}
\question[1] \tag{Algebra}
This is Question 1. This is tagged against Algebra.
\question[]
\begin{parts}
\part[1] \tag{Equations} This is Question 2a.This is tagged against Equations.
\part[1] \tag{Algebra} This is Question 2b.This is tagged against Algebra.
\end{parts}
\question[2] \tag{Data}
This is Question 3.This is tagged against Data.
\question[]
\begin{parts}
\part[1] \tag{Equations} This is Question 4a.This is tagged against Equations.
\part[1] \tag{Data} This is Question 4b.This is tagged against Data.
\end{parts}
\question[2] \tag{Algebra}
This is Question 5.This is tagged against Algebra.
\question[2] \tag{Data}
This is Question 6.This is tagged against Data.
\end{questions}
\taglist{Algebra,Data,Equations}
\end{document}
The desired result for the above code is below.
Update 1:
To include \subparts and suppress \parts point values.
\documentclass[addpoints]{exam}
\usepackage{tikz}% foreach and pgfmath
\makeatletter
\let\normal@parts=\parts
\def\parts{\normal@parts
\let\normal@part=\@doitem
\let\@doitem=\my@part}
%
\newcommand{\my@part}[1][\@empty]{% store points by part
\ifx\@empty#1
\expandafter\normal@part
\else
\stepcounter{partno}%
\immediate\write\@auxout{\string\gdef\string\pointsofp@\roman{question}@\roman{partno}{#1}}%
\addtocounter{partno}{-1}%
\expandafter\normal@part\expandafter[\expandafter#1\expandafter]%
\fi}
\newcommand{\tag}[1]{\ifnum\@listdepth=1
\expandafter\gdef\csname tagofq@\arabic{question}\endcsname{#1}%
\else
\expandafter\gdef\csname tagofp@\arabic{question}@\arabic{partno}\endcsname{#1}%
\fi}
\newcommand{\qlist}{}% reserve global name
\newcommand{\pointsum}{}
\newcommand{\addtoqlist}[1]{% #1 = \thequestion etc
\ifx\empty\qlist\relax
\xdef\qlist{#1}%
\else
\xdef\qlist{\qlist, #1}%
\fi}
\newif{\ifpart}
\newcommand{\taglist}[1]{% #1 = comma delimmited list of tags (in order) for summary
\@ifundefined{exam@numquestions}{}{\par%
\bgroup% use local definitions
\lineskip=0pt
\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut Tag}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut Question}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut Points}}\newline
\foreach \x in {#1} {\setcounter{question}{0}% loop over tags
\global\let\qlist=\empty
\xdef\pointsum{0}%
\loop\ifnum\value{question}<\exam@numquestions\relax% loop over questions
\stepcounter{question}%
\@ifundefined{tagofq@\arabic{question}}{% no tag on question
\setcounter{partno}{0}\parttrue
\bgroup\loop% llop over parts
\stepcounter{partno}%
\@ifundefined{r@part@\arabic{question}@\arabic{partno}}{\partfalse}{}%
\ifpart
\edef\thistag{\csname tagofp@\arabic{question}@\arabic{partno}\endcsname}%
\ifx\x\thistag\relax
\addtoqlist{\thequestion\thepartno}%
\edef\thispoints{\csname pointsofp@\roman{question}@\roman{partno}\endcsname}%
\pgfmathparse{int(\pointsum+\thispoints)}%
\global\let\pointsum=\pgfmathresult
\fi
\repeat
\egroup
}{% tag on question
\edef\thistag{\csname tagofq@\arabic{question}\endcsname}%
\ifx\x\thistag\relax
\addtoqlist{\thequestion}%
\edef\thispoints{\csname pointsofq@\roman{question}\endcsname}%
\pgfmathparse{int(\pointsum+\thispoints)}%
\global\let\pointsum=\pgfmathresult
\fi}%
\repeat
\vskip-\fboxrule\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut\x}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\qlist}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\pointsum}}\newline}%
\vskip-\fboxrule\noindent
\fbox{\parbox[t][1cm][t]{4cm}{\strut Total}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut}}\hspace{-\fboxrule}%
\fbox{\parbox[t][1cm][t]{4cm}{\strut\exam@numpoints}}
\egroup}}
\makeatother
\newcommand{\hidepoints}{%
\pointsinmargin\pointformat{}
}
\newcommand{\showpoints}{%
\nopointsinmargin\pointformat{(\thepoints)}
}
\begin{document}
\begin{questions}
\question[1] \tag{Algebra}
This is Question 1. This is tagged against Algebra.
\question
\begin{parts}
\hidepoints
\part[2] \tag{Equations} % I want to suppress and not include in total points this which is the sum of the subparts below.
\showpoints
\begin{subparts}
\subpart[1]This is Question 2a (2ai).This is tagged against Equations.
\subpart[1]This is Question 2a (2aii).This is tagged against Equations.
\end{subparts}
\part[1] \tag{Algebra} This is Question 2b.This is tagged against Algebra.
\end{parts}
\question[2] \tag{Data}
This is Question 3.This is tagged against Data.
\question
\begin{parts}
\part[1] \tag{Equations} This is Question 4a.This is tagged against Equations.
\part[1] \tag{Data} This is Question 4b.This is tagged against Data.
\end{parts}
\question[2] \tag{Algebra}
This is Question 5.This is tagged against Algebra.
\question[2] \tag{Data}
This is Question 6.This is tagged against Data.
\end{questions}
\taglist{Algebra,Data,Equations}
\end{document}
But this runs into the following issues when compiling gradetable.
As you can see the total don't add up to the total tags.
Best Answer
This version loops over subparts as well. Questions etc. with no points are not included in
\qlist. Question etc. with no tag inherit the tag of their parent. A\tagoutsidequestionswill create a default tag.If all the subparts have the same tag, only the part will be added to list of questions.