Perform spreadsheet-like calculations and display formula and result

Question

Currently I am performing calculations using excel and manually formatting them for printing using an online LaTeX equation editor. The end result looks something like this:

As you may imagine this requires a lot of double-hadling of the parameters and, if any of the variables change, everything must be retyped. Is there any way where I could achieve a similar output directly through LaTeX?

I would like to be able to define the variables, some of which are calculated from other variables, and display the formulas, with both the parameters and the values shown. I don't need to perform any complex mathematics. Typically +,-,*,/ and exponents is all that would be required though basic functions (sin, ln, log) may also be useful.

Answer 1

I started working on it before JPi had answered, so I will post my solution anyways.

LuaTeX is ideal for this. For example, here is solution using ConTeXt (It should be easy to translate it to LaTeX).

\startluacode
  userdata = userdata or {}
  userdata.variables = 
    {
      m = 10,
      Cp = 30,
      T1 = 15,
      T2 = 20,
    }

  variables = userdata.variables

  variables.DeltaT = variables.T2 - variables.T1
  variables.Q = variables.m*variables.Cp*variables.DeltaT

  local function showRow(a,b,c)
      context("\\NC %s \\NC %s \\NC %s \\NC \\NR", a, b, c)
  end

  local function singleRow(a)
      context("\\NC[nc=3, align=middle] %s \\NC \\NR", a)
  end

  local format = string.format

  userdata.ShowVariables = function()
    context.startTABLE{setups="table:variables"}
    showRow("Parameter Value", "Units", "Description")
    showRow("$m$", format("\\unit{%s KiloGram}", variables.m), "Mass")
    showRow("$Cp$", format("\\unit{%s KiloJoule/Celsius KiloGram}", variables.Cp), "Heat Capacity")
    showRow("$T_1$", format("\\unit{%s Celsius}", variables.T1), "Initial Temperature")
    showRow("$T_2$", format("\\unit{%s Celsius}", variables.T2), "Final Temperature")
    singleRow(format("$ΔT = T_2 - T_1 = %s - %s = %s~[\\unit{Celsius}]$", variables.T2, variables.T1, variables.DeltaT))
    showRow("$ΔT$", format("\\unit{%s Celsius}", variables.DeltaT), "Temperature Difference")
    singleRow(format("$Q = m × Cp × ΔT = %s × %s × %s = %s~[\\unit{KiloJoule}]$", variables.m, variables.Cp, variables.DeltaT, variables.Q))
    showRow("$Q$", format("\\unit{%s KiloJoule}", variables.Q), "Heat")
    context.stopTABLE()
  end
\stopluacode

\startsetups table:variables
  \setupTABLE[frame=off, offset=0.25em]
  \setupTABLE[column][3][width=12em] 
  % Width needed, otherwise column span doesn't work
\stopsetups

\define\ShowVariables{\ctxlua{userdata.ShowVariables()}}

\starttext
\ShowVariables
\stoptext

which gives

I used a separate namespace userdata to avoid conflict with existing variable names.

Answer 2

Easy with lualatex:

%% compile with lualatex
\documentclass{article}

\usepackage{luacode}

\begin{luacode*}
 function celsius(t)
  tex.sprint((t-32)*5/9)
  end
\end{luacode*}
\newcommand{\celsius}[1]{\luadirect{celsius(\luastring{#1})}}

\begin{document}

\begin{tabular}{rr}
 50 & \celsius{50}\\
 -40 & \celsius{-40}
 \end{tabular}

 \end{document}

Answer 3

• Currently I am performing calculations using excel and manually formatting them for printing using an online LaTeX equation editor.

• tranquillity, LaTeX itself is the system for graphical representation of the math expression if we talk about math part of LaTeX. The most of programs that perform the calculations by LaTeX it needs to be the LaTeX text typed with special rules. Each program has its own rules. Then such a program parses the text, recognizes variables, their values and make the calculations. As an algorithm it always like the sequence of the following operations:
• Typset LaTeX text of the special type were is specially specified such data as variables, their values, output format and so on;
• launch the program that perform the cslculation.
• I wish to offer a different solution. It seems there is exactly what you are looking for. That is the program that build the LaTeX string of math expression that you type in plain text easily. It performs calculations with variables, saves result to file, analyzes errors connected not only with wrong syntax, but it help find and even avoid such errors as loss of relevance (accuracy), and the possibility of accidental results (infinity, not a number).
• That program is AnEasyCalc. Type in any search engin (without spaces) and you will find a lot of file storage servers when it can be downloaded.

You can find it also at developer's site: http://steamandwater.od.ua/AnEasyCalc/index.html

• This demo version is unlimited by the use time, but has a limmited functionality. The main restriction is the sting length that can not be more 32. If we abandon long names and indexes fairly complex things can be calculated.

Good luck)