Graphics, Figures & Tables ⇒ Fractional Tick Marks on Number Lines

[LaTexLearner]

I've recently finished moving and am now back to learning LaTeX and TikZ!

I want to create a number line from 0 to 3 with tick marks at every, say, 1/2 or 1/3 or whatever.

I have figured out how to make the whole number part of the number line, but can't figure out the fractional tick marks. How do I improve on the following?

CODE THAT DID NOT WORK

Code: Select all

\documentclass[border=10pt]{article}

\usepackage{tikz}

\begin{document}

%THIS PICTURE OF THIRDS DOES NOT WORK.
%Can you not use fractions in the "foreach" command? 
%If not, do I have to approximate with decimals (see below in post)
\begin{tikzpicture}[scale=2]
  \draw[-latex] (0,0) -- (4.5,0); % the x-axis
  \foreach \x in  {0/3,1/3,...,12/3} % tick marks for every 1/3
    \draw (\x,4pt) -- (\x,-4pt);
  \foreach \x in {0,...,4} % the whole numbers labels
    \node [below] at (\x,-0.2) {$\x$};
\end{tikzpicture}

\end{document}

CODE THAT WORKED IN TERMS OF A ROUGH PICTURE, BUT SEEMS NON-ELEGANT AND CONTAINS ROUNDING ERRORS

Code: Select all

\documentclass[border=10pt]{article}

\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[scale=2]
  \draw[-latex] (0,0) -- (4.5,0); % the x-axis
  \foreach \x in  {0,0.33,0.67,1,1.33,1.67,2,2.33,2.67,3,3.33,3.67,4} % tick marks for every approx. 1/3
    \draw (\x,4pt) -- (\x,-4pt);
  \foreach \x in {0,...,4} % the whole numbers labels
    \node [below] at (\x,-0.2) {$\x$};
\end{tikzpicture}

\end{document}

[rais]

I have figured out how to make the whole number part of the number line, but can't figure out the fractional tick marks. How do I improve on the following?

Isn't the /-character used by the \foreach command as separator between different values (for the same run)?

You could try sth. like

Code: Select all

\documentclass{article}

\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[scale=2]
  \draw[-latex] (0,0) -- (4.5,0); % the x-axis
  \foreach \x in  {0,1,...,12} % tick marks for every 1/3
    \draw (\x/3,2pt) -- +(0,-4pt);
  \foreach \x in {0,...,4} % the whole numbers labels
    \draw (\x,4pt) -- +(0,-8pt) node [below] {$\x$};
\end{tikzpicture}

\end{document}

KR
Rainer

[LaTexLearner]

Isn't the /-character used by the \foreach command as separator between different values (for the same run)?

I'm not sure what you mean by this but...

I have figured out how to make the whole number part of the number line, but can't figure out the fractional tick marks. How do I improve on the following?

Isn't the /-character used by the \foreach command as separator between different values (for the same run)?

You could try sth. like

Code: Select all

\documentclass{article}

\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[scale=2]
  \draw[-latex] (0,0) -- (4.5,0); % the x-axis
  \foreach \x in  {0,1,...,12} % tick marks for every 1/3
    \draw (\x/3,2pt) -- +(0,-4pt);
  \foreach \x in {0,...,4} % the whole numbers labels
    \draw (\x,4pt) -- +(0,-8pt) node [below] {$\x$};
\end{tikzpicture}

\end{document}

KR
Rainer

... I completely understand this code. Thank you!

So, fractions CAN go in the \draw command but not in the \foreach command. Is that right?

[rais]

Isn't the /-character used by the \foreach command as separator between different values (for the same run)?

I'm not sure what you mean by this but...

well, consider this code snippet:

Code: Select all

\foreach \x/\y in {1/2, 3/4, 5/6}

now there's two variables---\x and \y---to be considered for the \foreach command...

So, fractions CAN go in the \draw command but not in the \foreach command. Is that right?

Not exactly. You could `hide' the /-character from the \foreach command by surrounding each fraction by an additional pair of braces, such as

Code: Select all

\foreach \x in {{1/3},{2/3},{3/3}}

KR
Rainer

[LaTexLearner]

So, fractions CAN go in the \draw command but not in the \foreach command. Is that right?

Not exactly. You could `hide' the /-character from the \foreach command by surrounding each fraction by an additional pair of braces, such as

Code: Select all

\foreach \x in {{1/3},{2/3},{3/3}}

KR
Rainer

Problem semi-fixed. Two issues remain for me.

First, it seems that when I add those extra braces, it loses the "math layout" that I want, i.e. I want the fractions on top of the number line to have a horizontal fraction bar.

Also, it seems unable to see that I am counting by halves in the \foreach command

Code: Select all

\documentclass[12pt,letterpaper]{article}

\usepackage{tikz}
\usetikzlibrary{arrows}

\begin{document}

\begin{tikzpicture}[scale=3]

% x-Axis
\draw[-latex] (0,0)--(4.5,0);

% Whole number labels below
\foreach \x in {0,1,2,3,4}
  \node [below] at (\x,-.15) {$\x$};

% DID NOT WORK IN GETTING FRACTION NUMBERS ABOVE AXIS
% COULD NOT SEE COUNTING BY HALVES?
% \foreach \x in { {0/2},{1/2},{2/2},{3/2},...,{8/2}  }
%   \node [above] at (\x,0.15) {$\x$};

% DID WORK IN GETTING FRACTION NUMBERS ABOVE AXIS
% BUT HAD TO WRITE OUT ALL THE HALVES
% AND DID NOT GET FRACTION WITH HORIZONTAL FRACTION BAR
\foreach \x in { {0/2},{1/2},{2/2},{3/2},{4/2},{5/2},{6/2},{7/2},{8/2}  }
  \node [above] at (\x,0.15) {$\x$};


\end{tikzpicture}

\end{document}

[LaTexLearner]

Another side comment: Why does the tikz picture indent?

Since I know I won't need that, should I write a macro to turn that off?

[rais]

First, it seems that when I add those extra braces, it loses the "math layout" that I want, i.e. I want the fractions on top of the number line to have a horizontal fraction bar.

Well, if you don't want to rip your \x apart to split it into denominator and numerator, use two variables.

Also, it seems unable to see that I am counting by halves in the \foreach command

Yes, the additional braces seem to hide more from \foreach than they were supposed to.
Back to the original approach, you'd just need a second variable---say, \y---for the denominator.
Since it would be constant (2 for halves), it doesn't need to show up in the \foreach statement.

Another side comment: Why does the tikz picture indent?

If it's not the normal first-line-of-a-paragraph-indent that you mean (where you could put a \noindent directly in front of the {tikzpicture} environment): you put a node at x=0. Each node is surrounded by space; you may want to look up `inner sep' in the tikz manual. Here, I just made it visible with the fill option:

Code: Select all

\documentclass[12pt,letterpaper]{article}

\usepackage{tikz}
\usetikzlibrary{arrows}

\begin{document}

\begin{tikzpicture}[scale=3]

% x-Axis
\draw[-latex] (0,0)--(4.5,0);

% Whole number labels below
\foreach \x in {0,1,2,3,4}
  \node [below, fill=cyan] at (\x,-.15) {$\x$};

\def\y{2}% the denominator
\foreach \x in {0,1,...,8}% and here just the numerator
  \node [above] at (\x/\y,0.15) {$\frac{\x}{\y}$};

\end{tikzpicture}

\end{document}

KR
Rainer

[LaTexLearner]

Got it. Thanks!

Next question.

I am trying to put in answer spaces above the number line. Why did the first code fail why the second code worked? Can there be only one \draw command under a \foreach command?

CODE THAT FAILED

Code: Select all

\begin{tikzpicture}[scale=3]

% x-axis
\draw (0,0)--(4,0);

%Make x-axis into rectangle that can be shaded
\draw (0,0.1)--(4,0.1);

% vertical tick marks for fifths
\foreach \x in {0,...,20}
   \draw (\x/5,-0.1)--(\x/5,0.1);

\foreach \x in {0,...,4}
   \node [below] at (\x,-0.1) {\x};
   
% ANSWER SPACES THAT DID NOT WORK
\foreach \x in {0,...,20}
  \draw[thin, gray] (\x/5-0.09,0.2)--(\x/5-0.09,0.45)--(\x/5+0.09,0.45)--(\x/5+0.09,0.2)--cycle;
  \draw[thin, gray, -latex] (\x/5,0.2)--(\x/5,0.12);
   
\end{tikzpicture}

CODE THAT WORKED

Code: Select all

\begin{tikzpicture}[scale=3]

% x-axis
\draw (0,0)--(4,0);

%Make x-axis into rectangle that can be shaded
\draw (0,0.1)--(4,0.1);

% vertical tick marks for fifths
\foreach \x in {0,...,20}
   \draw (\x/5,-0.1)--(\x/5,0.1);

\foreach \x in {0,...,4}
   \node [below] at (\x,-0.1) {\x};
   % ANSWER SPACES THAT DID WORK
\foreach \x in {0,...,20}
  \draw[thin, gray] (\x/5-0.09,0.2)--(\x/5-0.09,0.45)--(\x/5+0.09,0.45)--(\x/5+0.09,0.2)--cycle;

\foreach \x in {0,...,20}
   \draw[thin, gray, -latex] (\x/5,0.2)--(\x/5,0.12);
   
\end{tikzpicture}

[rais]

I am trying to put in answer spaces above the number line. Why did the first code fail why the second code worked? Can there be only one \draw command under a \foreach command?

The general syntax is \foreach <variable> in {<list of values>} <commands>. Inside the <commands>, the <variable> will be assigned to the different values. If the <commands> do not start with a brace, everything up to the next semicolon is used as <commands>.

So in your case,

Code: Select all

\foreach \x in {0,...,20}{%<--
  \draw[thin, gray] (\x/5-0.09,0.2)--(\x/5-0.09,0.45)--(\x/5+0.09,0.45)--(\x/5+0.09,0.2)--cycle;
  \draw[thin, gray, -latex] (\x/5,0.2)--(\x/5,0.12);
}%<--

should do.

KR
Rainer

[LaTexLearner]

Got it. Thank you!

I need to start learning all the "defaults" of LaTeX and TikZ, i.e. what the code assumes I want if I don't type anything...