7

I am interested in creating Pascal's triangle with Tikz and LaTeX. I would like to add a column of text on the left of the triangle, with header "Row Number" and then the entries of each row. I am new to Tikz and had trouble creating a structure like this on my own.

Like this (center justified triangle, not left aligned)

Row 0: 1
Row 1: 1
Row 2: 1 2 1
Row 3: 1 3 3 1
Row 4: 1 4 6 4 1
Row 5: 1 5 10 10 5 1
Row 6: 1 6 15 20 15 6 1
Row 7: 1 7 21 35 35 21 7 1
Row 8: 1 8 28 56 70 56 28 8 1
Row 9: 1 9 36 84 126 126 84 36 9 1
Row 10: 1 10 45 120 210 252 210 120 45 10 1

This code generated ideas, though since I am new to tikz, I wasn't sure where to go with it.

Pascal's triangle in tikz

Thanks!

Community
  • 1
Natalya
  • 225
  • Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – Paul Gessler Jul 08 '14 at 04:27
  • 2
    I have a follow-up question. Is it possible to do Mark's solution with symbols in Pascal's triangle? So, I could create the same figure, but instead of numbers, I would generate Pascal's triangle with ${\n \choose \k}$ at each node. – Natalya Jul 21 '14 at 01:57

2 Answers2

7

The following should do it. By using the fpu library it is possible to go beyond the usual limit of 17 rows in PGF.

\documentclass[tikz,border=5]{standalone}
\usepgflibrary{fpu}
\begin{document}
\def\N{10}
\tikz[x=0.75cm,y=0.5cm, 
  pascal node/.style={font=\footnotesize}, 
  row node/.style={font=\footnotesize, anchor=west, shift=(180:1)}]
  \path  
    \foreach \n in {0,...,\N} { 
      (-\N/2-1, -\n) node  [row node/.try]{Row \n:}
        \foreach \k in {0,...,\n}{
          (-\n/2+\k,-\n) node [pascal node/.try] {%
            \pgfkeys{/pgf/fpu}%
            \pgfmathparse{round(\n!/(\k!*(\n-\k)!))}%
            \pgfmathfloattoint{\pgfmathresult}%
            \pgfmathresult%
          }}};
\end{document}

enter image description here

Mark Wibrow
  • 70,437
4

Run with lualatex (the number of rows is not limited):

\documentclass[border=5]{standalone}
\usepackage{luacode,array}
\def\PascalTriangle#1{\directlua{PascalTriangle(#1)}}
\begin{luacode}
function nextrow(t)
  local ret = {}
  t[0], t[#t+1] = 0, 0
  for i = 1, #t do ret[i] = t[i-1] + t[i] end
  return ret
end

function PascalTriangle(n)
  tex.sprint("\\tabular{@{}lc@{}}")
  t = {1}
  tex.sprint("Row 0: & 1 \\\\")
  for i=1,n do
    t = nextrow(t)
    tex.print("Row "..i..": & ")
    for j=1,i+1 do tex.print("\\makebox[2em]{"..tostring(t[j]).."}") end 
    -- tex.sprint(tostring(unpack(t))) -- does not work
    tex.sprint("\\\\")
  end
  tex.sprint("\\endtabular")
end
\end{luacode}
\begin{document}
\footnotesize
\PascalTriangle{5}

\bigskip
\PascalTriangle{15}

\end{document}

enter image description here