Cfrgtkky

I have a set of two nodes and I would like to draw tight ellipses around them in my tikz picture. Note that this is part of a beamer presentation.

I have attached an image that illustrates the wanted effect.

Here is what I have so far:

documentclass[10pt,aspectratio=1610]{beamer}

usepackage{tikz}

usetikzlibrary{shapes,arrows,backgrounds,fit,positioning}



begin{document}



tikzset{res/.style={ellipse,draw,minimum height=0.5cm,minimum width=0.8cm}}

tikzset{literal/.style={rectangle,draw,minimum height=0.5cm,minimum width=0.8cm,text width = 1.2 cm, align = center}}



begin{frame}[fragile]{Example}{}

begin{tikzpicture}[node distance = 2 cm,auto, ]

node[res,] (obs1) {footnotesize :obs1} ;

node[res, left = 1cm of obs1] (shop1) {footnotesize :shop1} ;

node[literal, left = 1cm of shop1] (shopName1) {footnotesize ``Barnes & Noble''} ;

node[res, above of = shop1] (book1) {footnotesize :book1} ;

node[literal, left = 1cm of book1] (bookName1) {footnotesize ``Dune''} ;

node[res, below of = obs1] (obs2) {footnotesize :obs2} ;

node[res, left = 1cm of obs2] (shop2) {footnotesize :shop2} ;

node[literal, left = 1cm of shop2] (shopName2) {footnotesize ``Amazon''} ;

node[res, below of = shop2] (book2) {footnotesize :book2} ;

node[literal, left = 1cm of book2] (bookName2) {footnotesize ``Dracula''} ;

node[literal, below of = obs2] (measure2) {footnotesize 12} ;

node[literal, above of = obs1] (measure1) {footnotesize 7} ;

node[literal, right = 1cm of obs1] (monthName) {footnotesize ``January''} ;

node[literal, right = 1cm of measure1] (yearNum) {footnotesize ``2016''} ;

node[res, right = 1cm of monthName] (month) {footnotesize :january2016} ;

node[res, above of = month] (year) {footnotesize :2016} ;

node[res, below of = month] (day) {footnotesize :date31012016} ;



path[->,draw]

    (obs1) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :shop} (shop1)

    (obs2) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :shop} (shop2)



    (obs1) edge node[midway,above=-6pt,fill=white] {footnotesize :book} (book1)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :book} (book2)



    (book1) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :name} (bookName1)

    (book2) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :name} (bookName2)



    (shop1) edge node[midway,above=-6pt,fill=white] (title1) {footnotesize :title} (shopName1)

    (shop2) edge node[midway,above=-6pt,fill=white] (title2) {footnotesize :title} (shopName2)



    (obs1) edge node[midway,above=-6pt,fill=white] {footnotesize :price} (measure1)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :price} (measure2)



    (obs1) edge node[midway,above=-6pt,fill=white]  {footnotesize :date} (day)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :date} (day)



    (day) edge node[midway,above=-6pt,fill=white] {footnotesize skos:broader} (month)

    (month) edge node[midway,above=-6pt,fill=white] {footnotesize skos:broader} (year)



    (month) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :month} (monthName)

    (year) edge node[midway,above=-6pt,fill=white] {footnotesize :year} (yearNum)

    ;



begin{pgfonlayer}{background}

  node[fit=(shopName1)(shop1), fill=violet!30,ellipse] {};

  node[fit=(shopName2)(shop2), fill=violet!30,ellipse] {};

  node[fit=(bookName2)(book2), fill=violet!30,ellipse] {};

  node[fit=(bookName1)(book1), fill=violet!30,ellipse] {};

  node[fit=(measure1)(obs1), fill=blue!30,ellipse] {};

  node[fit=(measure2)(obs2), fill=blue!30,ellipse] {};

  node[fit=(year)(yearNum), fill=green!30,ellipse] {};

  node[fit=(month)(monthName), fill=green!30,ellipse] {};

end{pgfonlayer}

end{tikzpicture}

end{frame}

end{document}

Here is the result that it produce

Note how the ellipses do not fit the nodes but cover much more.
How can I create a tight ellipse around a pair of nodes?

If Jake's answer doesn't like or doesn't work for you, may be you could consider other shapes like rounded rectangle or just a rectangle with rounded corners.

Following code uses rounded rectangles for horizontal associations. As I could not manage to build a vertical rounded rectangle and cylinders doesn't fit very well, two rectangles with rounded corners are used for vertical associations.

documentclass[10pt,aspectratio=1610]{beamer}

usepackage{tikz}

usetikzlibrary{shapes,arrows,backgrounds,fit,positioning}



begin{document}



tikzset{res/.style={ellipse,draw,minimum height=0.5cm,minimum width=0.8cm}}

tikzset{literal/.style={rectangle,draw,minimum height=0.5cm,minimum width=0.8cm,text width = 1.2 cm, align = center}}

tikzset{hfit/.style={rounded rectangle, inner xsep=0pt, fill=#1!30},

           vfit/.style={rounded corners, fill=#1!30}}



begin{frame}[fragile]{Example}{}

begin{tikzpicture}[node distance = 2 cm,auto, ]

node[res,] (obs1) {footnotesize :obs1} ;

node[res, left = 1cm of obs1] (shop1) {footnotesize :shop1} ;

node[literal, left = 1cm of shop1] (shopName1) {footnotesize ``Barnes & Noble''} ;

node[res, above of = shop1] (book1) {footnotesize :book1} ;

node[literal, left = 1cm of book1] (bookName1) {footnotesize ``Dune''} ;

node[res, below of = obs1] (obs2) {footnotesize :obs2} ;

node[res, left = 1cm of obs2] (shop2) {footnotesize :shop2} ;

node[literal, left = 1cm of shop2] (shopName2) {footnotesize ``Amazon''} ;

node[res, below of = shop2] (book2) {footnotesize :book2} ;

node[literal, left = 1cm of book2] (bookName2) {footnotesize ``Dracula''} ;

node[literal, below of = obs2] (measure2) {footnotesize 12} ;

node[literal, above of = obs1] (measure1) {footnotesize 7} ;

node[literal, right = 1cm of obs1] (monthName) {footnotesize ``January''} ;

node[literal, right = 1cm of measure1] (yearNum) {footnotesize ``2016''} ;

node[res, right = 1cm of monthName] (month) {footnotesize :january2016} ;

node[res, above of = month] (year) {footnotesize :2016} ;

node[res, below of = month] (day) {footnotesize :date31012016} ;





path[->,draw]

    (obs1) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :shop} (shop1)

    (obs2) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :shop} (shop2)



    (obs1) edge node[midway,above=-6pt,fill=white] {footnotesize :book} (book1)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :book} (book2)



    (book1) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :name} (bookName1)

    (book2) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :name} (bookName2)



    (shop1) edge node[midway,above=-6pt,fill=white] (title1) {footnotesize :title} (shopName1)

    (shop2) edge node[midway,above=-6pt,fill=white] (title2) {footnotesize :title} (shopName2)



    (obs1) edge node[midway,above=-6pt,fill=white] {footnotesize :price} (measure1)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :price} (measure2)



    (obs1) edge node[midway,above=-6pt,fill=white]  {footnotesize :date} (day)

    (obs2) edge node[midway,above=-6pt,fill=white] {footnotesize :date} (day)



    (day) edge node[midway,above=-6pt,fill=white] {footnotesize skos:broader} (month)

    (month) edge node[midway,above=-6pt,fill=white] {footnotesize skos:broader} (year)



    (month) edge node[midway,above=-6pt,fill=white,inner sep=0pt] {footnotesize :month} (monthName)

    (year) edge node[midway,above=-6pt,fill=white] {footnotesize :year} (yearNum)

    ;



begin{pgfonlayer}{background}

  node[fit=(shopName1)(shop1), hfit=violet] {};

  node[fit=(shopName2)(shop2), hfit=violet] {};

  node[fit=(bookName2)(book2), hfit=violet] {};

  node[fit=(bookName1)(book1), hfit=violet] {};

  node[fit=(measure1)(obs1), vfit=blue] {};

  node[fit=(measure2)(obs2), vfit=blue] {};

  node[fit=(year)(yearNum), hfit=green] {};

  node[fit=(month)(monthName), hfit=green] {};

end{pgfonlayer}

end{tikzpicture}

end{frame}

end{document}

after some effort to make your code more consistent and shorter and define new node style FIT by which options you can define its inner sep according to your needs, i obtain the following result:

documentclass[10pt,aspectratio=1610]{beamer}

usepackage{tikz}

usetikzlibrary{arrows,

                backgrounds,

                fit,

                positioning,

                quotes,

                shapes}





begin{document}



begin{frame}[fragile]

frametitle{Example}

    begin{center}

    begin{tikzpicture}[

          scale = 0.95, transform shape,

  node distance = 22mm and 11mm,

     res/.style = {ellipse, draw, minimum height=0.5cm, minimum width=0.8cm,

                  font=footnotesize },

 literal/.style = {rectangle, draw, minimum height=0.5cm, text width=1.2 cm,

                  align=center, font=footnotesize},

FIT/.style args = {#1/#2/#3}{ellipse, fill=#1, inner xsep=#2, fit=#3},

every edge quotes/.style = {fill=white, inner sep=1pt, font=footnotesize},

                        ]

node[res] (obs1) {:obs1} ;

node[res, left = 1cm of obs1] (shop1) {:shop1} ;

node[literal, left = of shop1] (shopName1) {``Barnes & Noble''} ;

node[res, above of = shop1] (book1) {footnotesize :book1} ;

node[literal, left = of book1] (bookName1) {``Dune''} ;

node[res, below of = obs1] (obs2) {:obs2} ;

node[res, left = of obs2] (shop2) {:shop2} ;

node[literal, left = of shop2] (shopName2) {``Amazon''} ;

node[res, below of = shop2] (book2) {:book2} ;

node[literal, left = of book2] (bookName2) {``Dracula''} ;

node[literal, below of = obs2] (measure2) {12} ;

node[literal, above of = obs1] (measure1) {7} ;

node[literal, right = of obs1] (monthName) {``January''} ;

node[literal, right = of measure1] (yearNum) {``2016''} ;

node[res, right = of monthName] (month) {:january2016} ;

node[res, above = of month] (year) {:2016} ;

node[res, below = of month] (day) {:date31012016} ;



path[->,draw]

    (obs1) edge [":shop"] (shop1)

    (obs2) edge [":shop"] (shop2)



    (obs1)  edge [":book"] (book1)

    (obs2)  edge [":book"] (book2)



    (book1) edge [":name"] (bookName1)

    (book2) edge [":name"] (bookName2)



    (shop1) edge [name=title1,":title"] (shopName1)

    (shop2) edge [name=title2,":title"] (shopName2)



    (obs1)  edge [":price"] (measure1)

    (obs2)  edge [":price"] (measure2)



    (obs1)  edge [":date"] (day)

    (obs2)  edge [":date"] (day)



    (day)   edge ["skos:broader"] (month)

    (month) edge ["skos:broader"] (year)



    (month) edge [":month"]   (monthName)

    (year)  edge [":year"]    (yearNum)

    ;

begin{pgfonlayer}{background}

  node[FIT=violet!30/-2mm/(shopName1)(shop1)] {};

  node[FIT=violet!30/-2mm/(shopName2)(shop2)] {};

  node[FIT=violet!30/-2mm/(bookName2)(book2)] {};

  node[FIT=violet!30/-2mm/(bookName1)(book1)] {};

  node[FIT=blue!30/1mm/(measure1)(obs1),inner ysep=0mm] {};

  node[FIT=blue!30/1mm/(measure2)(obs2),inner ysep=0mm] {};

  node[FIT=blue!30/-3mm/(year)(yearNum),rotate=10] {};

  node[FIT=blue!30/-3mm/(month)(monthName)] {};

end{pgfonlayer}

end{tikzpicture}

    end{center}

end{frame}

end{document}

You can simply use the draw command in the tikz package. In the following example you have 6 nodes and two sets each including three of the nodes.

An ellipse is defined using "circle" and two radii, one in the x-direction and the other in the y-direction. According to your case, you can shift each ellipse using the coordinates of its origin that is defined just after the command draw.

The first draw command is there to draw some edges and have a graph.
Also, you can rotate an ellipse using the degrees, as is clear in the code.

The command begin{center}...end{center} is added to have the whole picture at the center of the page and is not obligatory; based on your case, you can remove it from the code.

begin{center}

tikzstyle{every node}=[circle, draw, fill=black,inner sep=0pt, minimum width=4pt,

node distance =1 cm and 1cm ] 

begin{tikzpicture}

    node (b)  [label=below:$ b $]{};

    node (a1) [label=left:$ a_{1} $, above left = 1cm and 2cm of b]{};

    node (a2) [label=left:$ a_{2} $, above = .5cm of a1]{};

    node (c1) [label=right:$ c_{1} $, above right = 1cm and 2cm of b]{};

    node (c2) [label=right:$ c_{2} $, above = .5cm of c1]{};

    node (d)  [label=above:$ d $, above left = 1cm and 2cm of c2]{};



    draw (d) -- (a1) -- (c1) -- (d) -- (a2) -- (c2) -- (d);

    draw (-1.2,.85) circle [x radius=2.3, y radius=1, rotate=150];

    draw (1.2,.85) circle [x radius=2.3, y radius=1, rotate=30];

 end{tikzpicture}

end{center}

Of course, you need to load the package tikz and make use of tikz's positioning library therein, i.e. the beginning of your document must look like the following

documentclass{"THE TYPE OF YOUR DOCUMENT,e.g.: thesis"}

.

.

.

usepackage{tikz}

usetikzlibrary {positioning}

.

.

.

begin{document}

The output can be seen in the following picture: