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Activities to Accompany Applied Combinatorics

Worksheet 6.3 Interval Representations to Diagrams

Activity 6.3.1.

Below are two collections of intervals. For each, draw the order diagram of the interval order represented by these intervals.

(a)

described in detail following the image
A collection of intervals. The intervals are displayed with a number line that allows identification of the endpoints of the intervals.
\begin{align*} a \amp = [6,6]\\ b \amp = [6,6]\\ c \amp = [1,3]\\ d \amp = [5,6]\\ e \amp = [1,1]\\ f \amp = [4,6]\\ g \amp = [4,5]\\ h \amp = [2,2]\\ i \amp = [3,4]\\ j \amp = [2,2] \end{align*}
Solution.
Diagram Exploration Keyboard Controls
Key Action
Enter, A Activate keyboard driven exploration
B Activate menu driven exploration
Escape Leave exploration mode
Cursor down Explore next lower level
Cursor up Explore next upper level
Cursor right Explore next element on level
Cursor left Explore previous element on level
X Toggle expert mode
W Extra details if available
Space Repeat speech
M Activate step magnification
Comma Activate direct magnification
N Deactivate magnification
Z Toggle subtitles
C Cycle contrast settings
T Monochrome colours
L Toggle language (if available)
K Kill current sound
Y Stop sound output
O Start and stop sonification
P Repeat sonification output
The order diagram of the poset whose interval representation was given. Annotations give cover relations for each of the points.

(b)

described in detail following the image
A collection of intervals labeled with letters from \(a\) to \(l\text{.}\) The intervals are not displayed with a number line. Using \(\ell(x)\) and \(r(x)\) to denote the left and right endpoints of the interval \(x\text{,}\) respectively, we have the following (strict) ordering of the endpoints
\begin{equation*} \ell(c) \lt \ell(d) \lt \ell(l) \lt r(d) \lt \ell(b)\lt r(b)\lt \ell(i)\lt r(c)\lt r(l)\lt \ell(h)\lt \ell(a)\lt r(h)\lt \ell(g)\lt r(a)\lt \ell(e)\lt r(g)\lt r(i)\lt \ell(f)\lt \ell(j)\lt r(e)\lt \ell(k)\lt r(f)\lt r(k)\lt r(j)\text{.} \end{equation*}
Solution.
Diagram Exploration Keyboard Controls
Key Action
Enter, A Activate keyboard driven exploration
B Activate menu driven exploration
Escape Leave exploration mode
Cursor down Explore next lower level
Cursor up Explore next upper level
Cursor right Explore next element on level
Cursor left Explore previous element on level
X Toggle expert mode
W Extra details if available
Space Repeat speech
M Activate step magnification
Comma Activate direct magnification
N Deactivate magnification
Z Toggle subtitles
C Cycle contrast settings
T Monochrome colours
L Toggle language (if available)
K Kill current sound
Y Stop sound output
O Start and stop sonification
P Repeat sonification output
The order diagram of the poset whose interval representation was given. Annotations give cover relations for each of the points.