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I have a tabular environment with a dozen or so itemized lines, each with a numeric integer cost. I would like to display a total in the last row. I've edited items in the table several times over a period of time, each time tediously recomputing the total.

Is there any way to have inline evaluation for a simple arithmetic formula, e.g. something akin to bash's $(()): The total is $((12 + 34 + 23 + ... + 5)) where the evaluated expression would be shown, rather than the literal equation. I'd be happy with changing an item's line value and also change the corresponding number in the equation (I don't think I need full spreadsheet expressiveness here).

I'd also rather not add a preprocessing step to generate the table from a template. The size of the table does not warrant that yet.

I figure there has to be a simple builtin way in tex to display the result of a calculation defined inline with the source document. By abusing a custom counter maybe, or by defining a new named length, adding units to it, and then displaying its value?

Trying to achieve something like this (pseudocode):

% initialize the current total to 0 before the table
{\thetotal = 0}

\begin{tabular}{@{}lp{4cm}r@{}} \toprule
  Store & Purpose & Items\\
  \midrule
  Safeway & for the salad   &    10 tomatoes  {\thetotal += 10} \\
  Whole Foods & for dessert &     4 muffins   {\thetotal += 4}  \\
  % ...
  % many more rows here.
  % in each row, \thetotal is incremented. This way, if I change
  % one line's value, I can change just that line and I don't need
  % to change anything else.
  % ...
  Home Depot & leftovers &     17 mouse traps {\thetotal += 17} \\
  \bottomrule
  % Lastly, show the value of the counter at that point in the document
  \multicolumn{2}{r}{Total} & \thetotal items
\end{tabular}

I would like the last row's last column to show the running tally at that point in the document, i.e., Total 31 in this example.

init_js
  • 257
  • it isn't clear how your inline expression question relates to table cells, you can do \the\numexpr 12 + 34 + 23 + 5\relax to typeset 74 but do you need to pick the values up from a table? – David Carlisle Apr 11 '17 at 23:02
  • I think this is what I need! As I said, I'm fine with some local duplication of numbers.

    Could I, next to each row, add to \numexpr, and display the tally on the last row?

     – init_js Apr 12 '17 at 00:20
  • made question more concrete with an example – init_js Apr 12 '17 at 00:30
  • @init_js: What should the last columns entries be? 10, 14, 31? – Werner Apr 12 '17 at 03:48
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    Maybe you can have a look at the spreadtab package. – egreg Apr 12 '17 at 08:27
  • @Werner : specified what the last line should be. @egreg : spreadtab looks like a winner too (although seems more complex than \numexpr) . Not sure if it allows display of table cells to be different than the number itself (e.g. display number 4 as "four"). edge case, admittedly. I'll give it a shot. If I end up writing a formal answer, I'll probably include both approaches.

    Anyone knows other quick and dirty tricks by defining custom lengths (I have a gut feeling there's a way there)?

     – init_js Apr 12 '17 at 22:52

1 Answers1

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Since only integer values are involved, the \addtocounter command should be sufficient.

I slightly changed the table and added the \additems command, that performs the calculation automatically. The final table design is left to the O.P. 

\documentclass{article}

\usepackage{booktabs}
\usepackage{siunitx}
\newcounter{total}
\newcommand{\additem}[2]{%
  \num{#1} & #2 &   \addtocounter{total}{#1} \thetotal
}

\begin{document}

\begin{tabular}{@{}lp{4cm}rlr@{}} \toprule
  Store & Purpose & \multicolumn{3}{c}{Items} \tabularnewline
  \midrule
  Safeway & for the salad   &    \additem{10}{tomatoes} \tabularnewline
  Whole Foods & for dessert &    \additem{4}{muffins}   \tabularnewline
  Home Depot & leftovers &     \additem{17}{mouse traps} \tabularnewline
  \bottomrule
  \multicolumn{4}{r}{Total} & \thetotal\ items
\end{tabular}


\end{document}

enter image description here

Another version without running sum

\documentclass{article}

\usepackage{booktabs}
\usepackage{siunitx}
\newcounter{total}
\newcommand{\additem}[2]{%
  \num{#1} & #2    \addtocounter{total}{#1} 
}

\begin{document}

\begin{tabular}{@{}lp{4cm}rl@{}} \toprule
  Store & Purpose & \multicolumn{2}{c}{Items} \tabularnewline
  \midrule
  Safeway & for the salad   &    \additem{10}{tomatoes} \tabularnewline
  Whole Foods & for dessert &    \additem{4}{muffins}   \tabularnewline
  Home Depot & leftovers &     \additem{17}{mouse traps} \tabularnewline
  \bottomrule
  \multicolumn{2}{r}{Total} & \thetotal & %items
\end{tabular}


\end{document}

enter image description here

  • Unfortunately 10 + 14 + 31 ≠ 31. – Werner Apr 12 '17 at 03:43
  • @Werner: The last column is the accumulated sum –  Apr 12 '17 at 03:43
  • Nicely put. The last non-running-total table is closer to what I had in mind, but I guess doing running totals where the counter approach shines over a single \numexpr 10 + 4 + 17 \relax at the end. – init_js Apr 18 '17 at 19:54
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    @init_js: \numexpr is an eTeX extension (which is activated for every up-to-date TeX distribution most likely anyway), but you still have to store the values to add in between, in order to retrieve them later on to inject them the to \numexpr primitive? Is that easier? Don't forgot that you would have to store the individual numbers globally since you're using them in table cell, which is a group. So this is exactly what \addtocounter does, a global addition if the local number is needed only for the summation but not for other purposes other than display later on. –  Apr 18 '17 at 20:02
  • This is perhaps a different question, but for floating point, would you abuse integer counters (e.g. $1.30 + $2.70 ~= (130 + 270) and move that period when displaying), or is there another arcane trick? I sensed you had something in mind. – init_js Apr 18 '17 at 20:18
  • @init_js: Of course, floating point numbers are not possible with an counter approach without tricks. But try (for fun) \the\numexpr 3.2 + 6.8\relax ;-) –  Apr 18 '17 at 20:21
  • @init_js: See for example a way for floating point numbers: https://tex.stackexchange.com/questions/196373/is-there-a-counter-or-variable-that-can-be-used-to-store-non-integers/285282?s=12|0.0000#285282, unfortunately, it did not receive much attention :-( –  Apr 18 '17 at 20:29