
\section{Number Printing}
\label{pgfmath-numberprinting}

{\emph{An extension by Christian Feuersänger}}

\medskip
\noindent
\pgfname\ supports number printing in different styles and rounds to arbitrary
precision.

\begin{command}{\pgfmathprintnumber\marg{x}}
    Generates pretty-printed output for the (real) number \meta{x}. The input
    number \meta{x} is parsed using |\pgfmathfloatparsenumber| which allows
    arbitrary precision.

    Numbers are typeset in math mode using the current set of number printing
    options, see below. Optional arguments can also be provided using
    |\pgfmathprintnumber[|\meta{options}|]|\meta{x}.
\end{command}

\begin{command}{\pgfmathprintnumberto\marg{x}\marg{macro}}
    Returns the resulting number into \meta{macro} instead of typesetting it
    directly.
\end{command}

\begin{key}{/pgf/number format/fixed}
    Configures |\pgfmathprintnumber| to round the number to a fixed number of
    digits after the period, discarding any trailing zeros.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}

    See section~\ref{sec:number:styles} for how to change the appearance.
\end{key}

\begin{key}{/pgf/number format/fixed zerofill=\marg{boolean}  (default true)}
    Enables or disables zero filling for any number drawn in fixed point
    format.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,fixed zerofill,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}
    %
    This key affects numbers drawn with |fixed| or |std| styles (the latter
    only if no scientific format is chosen).
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,std,fixed zerofill,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-05}\hspace{1em}
\pgfmathprintnumber{1}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}

    See section~\ref{sec:number:styles} for how to change the appearance.
\end{key}

\begin{key}{/pgf/number format/sci}
    Configures |\pgfmathprintnumber| to display numbers in scientific format,
    that means sign, mantissa and exponent (basis~$10$). The mantissa is
    rounded to the desired |precision| (or |sci precision|, see below).
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}

    See section~\ref{sec:number:styles} for how to change the exponential
    display style.
\end{key}

\begin{key}{/pgf/number format/sci zerofill=\marg{boolean}  (default true)}
    Enables or disables zero filling for any number drawn in scientific format.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci zerofill,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}
    %
    As with |fixed zerofill|, this option does only affect numbers drawn in
    |sci| format (or |std| if the scientific format is chosen).

    See section~\ref{sec:number:styles} for how to change the exponential
    display style.
\end{key}

\begin{stylekey}{/pgf/number format/zerofill=\marg{boolean} (default true)}
    Sets both |fixed zerofill| and |sci zerofill| at once.
\end{stylekey}

\begin{keylist}{/pgf/number format/std,%
    /pgf/number format/std=\meta{lower e},
    /pgf/number format/std=\meta{lower e}:\meta{upper e}%
}
    Configures |\pgfmathprintnumber| to a standard algorithm. It chooses either
    |fixed| or |sci|, depending on the order of magnitude. Let $n=s \cdot m
    \cdot 10^e$ be the input number and $p$ the current precision. If $-p/2 \le
    e \le 4$, the number is displayed using |fixed| format. Otherwise, it is
    displayed using |sci| format.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,std,precision=2}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}
    %
    The parameters can be customized using the optional integer argument(s): if
    $\text{\meta{lower e}} \le e \le \text{\meta{upper e}}$, the number is
    displayed in |fixed| format, otherwise in |sci| format. Note that
    \meta{lower e} should be negative for useful results. The precision used
    for the scientific format can be adjusted with |sci precision| if
    necessary.
\end{keylist}

\begin{keylist}{/pgf/number format/relative*=\meta{exponent base 10}}
    Configures |\pgfmathprintnumber| to format numbers relative to an order of
    magnitude, $10^r$, where $r$ is an integer number.

    This key addresses different use-cases.

    \paragraph{First use-case:}

    provide a unified format for a \emph{sequence} of numbers. Consider the
    following test:
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/relative*={1}}
\pgfmathprintnumber{6.42e-16}\hspace{1em}
\pgfmathprintnumber{1.2}\hspace{1em}
\pgfmathprintnumber{6}\hspace{1em}
\pgfmathprintnumber{20.6}\hspace{1em}
\pgfmathprintnumber{87}
\end{codeexample}
    %
    \noindent With any other style, the |6.42e-16| would have been formatted as
    an isolated number. Here, it is rounded to |0| because when viewed relative
    to $10^1$ (the exponent $1$ is the argument for |relative|), it has no
    significant digits.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/relative*={2}}
\pgfmathprintnumber{123.345}\hspace{1em}
\pgfmathprintnumber{0.0012}\hspace{1em}
\pgfmathprintnumber{0.0014}\hspace{1em}
\end{codeexample}
    %
    \noindent The example above applies the initial |precision=2| to |123.345|
    -- relative to $100$. Two significant digits of |123.345| relative to $100$
    are |123|. Note that the ``$2$ significant digits of |123.345|'' translates
    to ``round |1.2345| to $2$ digits'', which would yield |1.2300|. Similarly,
    the other two numbers are |0| compared to $100$ using the given
    |precision|.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/relative*={-3}}
\pgfmathprintnumber{123.345}\hspace{1em}
\pgfmathprintnumber{0.0012}\hspace{1em}
\pgfmathprintnumber{0.0014}\hspace{1em}
\end{codeexample}

    \paragraph{Second use-case:}

    improve rounding in the presence of \emph{inaccurate} numbers. Let us
    suppose that some limited-precision arithmetic resulted in the result
    |123456999| (like the |fpu| of \pgfname). You know that its precision is
    about five or six significant digits. And you want to provide a fixed point
    output. In this case, the trailing digits |....999| are a numerical
    artifact due to the limited precision. Use |relative*=3,precision=0| to
    eliminate the artifacts:
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,relative*={3},precision=0}
\pgfmathprintnumber{123456999}\hspace{1em}
\pgfmathprintnumber{123456999.12}
\end{codeexample}
    %
    \noindent Here, |precision=0| means that we inspect |123456.999| and round
    that number to $0$ digits. Finally, we move the period back to its initial
    position. Adding |relative style=fixed| results in fixed point output
    format:
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,relative*={3},precision=0,relative style=fixed}
\pgfmathprintnumber{123456999}\hspace{1em}
\pgfmathprintnumber{123456999.12}
\end{codeexample}
    %
    \noindent Note that there is another alternative for this use-case which is
    discussed later: the |fixed relative| style.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed relative,precision=6}
\pgfmathprintnumber{123456999}\hspace{1em}
\pgfmathprintnumber{123456999.12}
\end{codeexample}

    You might wonder why there is an asterisk in the key's name. The short
    answer is: there is also a \declareandlabel{/pgf/number format/relative}
    number printer which does unexpected things. The key |relative*| repairs
    this. Existing code will still use the old behavior.

    Technically, the key works as follows: as already explained above,
    |relative*=3| key applied to |123456999.12| moves the period by three
    positions and analyzes |123456.99912|. Mathematically speaking, we are
    given a number $x = \pm m \cdot 10^e$ and we attempt to apply
    |relative*=|$r$. The method then rounds $x / 10^r$ to |precision| digits.
    Afterwards, it multiplies the result by $10^r$ and typesets it.
\end{keylist}

\begin{stylekey}{/pgf/number format/every relative}
    A style which configures how the |relative| method finally displays its
    results.

    The initial configuration is
    %
\begin{codeexample}[code only]
\pgfkeys{/pgf/number format/every relative/.style=std}
\end{codeexample}

    Note that rounding is turned off when the resulting style is being
    evaluated (since |relative| already rounded the number).

    Although supported, I discourage from using |fixed zerofill| or
    |sci zerofill| in this context -- it may lead to a suggestion of higher
    precision than is actually used (because |fixed zerofill| might simply add
    |.00| although there was a different information before |relative| rounded
    the result).
\end{stylekey}

\begin{key}{/pgf/number format/relative style=\marg{options}}
    The same as |every relative/.append style=|\marg{options}.
\end{key}

\begin{keylist}{/pgf/number format/fixed relative}
    Configures |\pgfmathprintnumber| to format numbers in a similar way to the
    |fixed| style, but the |precision| is interpreted relatively to the
    number's exponent.

    The motivation is to get the same rounding effect as for |sci|, but to
    display the number in the |fixed| style:
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed relative,precision=3}
\pgfmathprintnumber{1000.0123}\hspace{1em}
\pgfmathprintnumber{100.0567}\hspace{1em}
\pgfmathprintnumber{0.000010003452}\hspace{1em}
\pgfmathprintnumber{0.010073452}\hspace{1em}
\pgfmathprintnumber{1.23567}\hspace{1em}
\pgfmathprintnumber{1003.75}\hspace{1em}
\pgfmathprintnumber{1006.75}\hspace{1em}
\end{codeexample}

    The effect of |fixed relative| is that the number is rounded to
    \emph{exactly} the first \meta{precision} non-zero digits, no matter how
    many leading zeros the number might have.

    Use |fixed relative| if you want |fixed| and if you know that only the
    first $n$ digits are correct. Use |sci| if you need a scientific display
    style and only the first $n$ digits are correct.

    Note that |fixed relative| ignores the |fixed zerofill| flag.

    See also the |relative*| key. Note that the |relative=|\marg{exponent} key
    explicitly moves the period to some designated position before it attempts
    to round the number. Afterwards, it ``rounds from the right'', i.e.\ it
    rounds to that explicitly chosen digit position. In contrast to that,
    |fixed relative| ``rounds from the left'': it takes the \emph{first}
    non-zero digit, temporarily places the period after this digit, and rounds
    that number. The rounding style |fixed| leaves the period where it is, and
    rounds everything behind that digit. The |sci| style is similar to 
    |fixed relative|.
\end{keylist}

\begin{key}{/pgf/number format/int detect}
    Configures |\pgfmathprintnumber| to detect integers automatically. If the
    input number is an integer, no period is displayed at all. If not, the
    scientific format is chosen.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,int detect,precision=2}
\pgfmathprintnumber{15}\hspace{1em}
\pgfmathprintnumber{20}\hspace{1em}
\pgfmathprintnumber{20.4}\hspace{1em}
\pgfmathprintnumber{0.01}\hspace{1em}
\pgfmathprintnumber{0}
\end{codeexample}
    %
\end{key}

\begin{command}{\pgfmathifisint\marg{number constant}\marg{true code}\marg{false code}}
    A command which does the same check as |int detect|, but it invokes
    \meta{true code} if the \meta{number constant} actually is an integer and
    the \meta{false code} if not.

    As a side-effect, |\pgfretval| will contain the parsed number, either in
    integer format or as parsed floating point number.

    The argument \meta{number constant} will be parsed with
    |\pgfmathfloatparsenumber|.
    %
\begin{codeexample}[]
15 \pgfmathifisint{15}{is an int: \pgfretval.}{is no int}\hspace{1em}
15.5 \pgfmathifisint{15.5}{is an int: \pgfretval.}{is no int}
\end{codeexample}
    %
\end{command}

\begin{key}{/pgf/number format/int trunc}
    Truncates every number to integers (discards any digit after the period).
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,int trunc}
\pgfmathprintnumber{4.568}\hspace{1em}
\pgfmathprintnumber{5e-04}\hspace{1em}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{24415.98123}\hspace{1em}
\pgfmathprintnumber{123456.12345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/frac}
    Displays numbers as fractionals.
    %
\begin{codeexample}[width=3cm,preamble={\usetikzlibrary{fpu}}]
\pgfkeys{/pgf/number format/frac}
\pgfmathprintnumber{0.333333333333333}\hspace{1em}
\pgfmathprintnumber{0.5}\hspace{1em}
\pgfmathprintnumber{2.133333333333325e-01}\hspace{1em}
\pgfmathprintnumber{0.12}\hspace{1em}
\pgfmathprintnumber{2.666666666666646e-02}\hspace{1em}
\pgfmathprintnumber{-1.333333333333334e-02}\hspace{1em}
\pgfmathprintnumber{7.200000000000000e-01}\hspace{1em}
\pgfmathprintnumber{6.666666666666667e-02}\hspace{1em}
\pgfmathprintnumber{1.333333333333333e-01}\hspace{1em}
\pgfmathprintnumber{-1.333333333333333e-02}\hspace{1em}
\pgfmathprintnumber{3.3333333}\hspace{1em}
\pgfmathprintnumber{1.2345}\hspace{1em}
\pgfmathprintnumber{1}\hspace{1em}
\pgfmathprintnumber{-6}
\end{codeexample}

    \begin{key}{/pgf/number format/frac TeX=\marg{\textbackslash macro} (initially \texttt{\textbackslash frac})}
        Allows to use a different implementation for |\frac| inside of the
        |frac| display type.
    \end{key}

    \begin{key}{/pgf/number format/frac denom=\meta{int} (initially empty)}
        Allows to provide a custom denominator for |frac|.
        %
\begin{codeexample}[width=3cm,preamble={\usetikzlibrary{fpu}}]
\pgfkeys{/pgf/number format/.cd,frac, frac denom=10}
\pgfmathprintnumber{0.1}\hspace{1em}
\pgfmathprintnumber{0.5}\hspace{1em}
\pgfmathprintnumber{1.2}\hspace{1em}
\pgfmathprintnumber{-0.6}\hspace{1em}
\pgfmathprintnumber{-1.4}\hspace{1em}
\end{codeexample}
    \end{key}
    %
    \begin{key}{/pgf/number format/frac whole=\mchoice{true,false} (initially true)}
        Configures whether complete integer parts shall be placed in front of
        the fractional part. In this case, the fractional part will be less
        then $1$. Use |frac whole=false| to avoid whole number parts.
        %
\begin{codeexample}[width=3cm,preamble={\usetikzlibrary{fpu}}]
\pgfkeys{/pgf/number format/.cd,frac, frac whole=false}
\pgfmathprintnumber{20.1}\hspace{1em}
\pgfmathprintnumber{5.5}\hspace{1em}
\pgfmathprintnumber{1.2}\hspace{1em}
\pgfmathprintnumber{-5.6}\hspace{1em}
\pgfmathprintnumber{-1.4}\hspace{1em}
\end{codeexample}
    \end{key}
    %
    \begin{key}{/pgf/number format/frac shift=\marg{integer} (initially 4)}
        In case you experience problems because of stability problems, try
        experimenting with a different |frac shift|. Higher shift values $k$
        yield higher sensitivity to inaccurate data or inaccurate arithmetic.

        Technically, the following happens. If $r < 1$ is the fractional part
        of the mantissa, then a scale $i = 1/r \cdot 10^k$ is computed where
        $k$ is the shift; fractional parts of $i$ are neglected. The value
        $1/r$ is computed internally, its error is amplified.

        If you still experience stability problems, use |\usepackage{fp}| in
        your preamble. The |frac| style will then automatically employ the
        higher absolute precision of |fp| for the computation of $1/r$.
    \end{key}
\end{key}

\begin{key}{/pgf/number format/precision=\marg{number}}
    Sets the desired rounding precision for any display operation. For
    scientific format, this affects the mantissa.
\end{key}

\begin{key}{/pgf/number format/sci precision=\meta{number or empty} (initially empty)}
    Sets the desired rounding precision only for |sci| styles.

    Use |sci precision={}| to restore the initial configuration (which uses the
    argument provided to |precision| for all number styles).
\end{key}

\begin{key}{/pgf/number format/read comma as period=\mchoice{true,false} (initially false)}
    This is one of the few keys which allows to customize the number parser. If
    this switch is turned on, a comma is read just as a period.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/read comma as period}
\pgfmathprintnumber{1234,56}
\end{codeexample}
    %
    This is typically undesired as it can cause side-effects with math parsing
    instructions. However, it is supported to format input numbers or input
    tables. Consider |use comma| to typeset the result with a comma as well.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    read comma as period,
    use comma}
\pgfmathprintnumber{1234,56}
\end{codeexample}
    %
\end{key}


\subsection{Changing display styles}%
\label{sec:number:styles}

You can change the way how numbers are displayed. For example, if you use the
`\texttt{fixed}' style, the input number is rounded to the desired precision
and the current fixed point display style is used to typeset the number. The
same is applied to any other format: first, rounding routines are used to get
the correct digits, afterwards a display style generates proper \TeX-code.

\begin{key}{/pgf/number format/set decimal separator=\marg{text}}
    Assigns \marg{text} as decimal separator for any fixed point numbers
    (including the mantissa in sci format).

    Use |\pgfkeysgetvalue{/pgf/number format/set decimal separator}\value| to
    get the current separator into |\value|.
\end{key}

\begin{stylekey}{/pgf/number format/dec sep=\marg{text}}
    Just another name for |set decimal separator|.
\end{stylekey}

\begin{key}{/pgf/number format/set thousands separator=\marg{text}}
    Assigns \marg{text} as thousands separator for any fixed point numbers
    (including the mantissa in sci format).
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,
    precision=2,
    set thousands separator={}}
\pgfmathprintnumber{1234.56}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,
    precision=2,
    set thousands separator={}}
\pgfmathprintnumber{1234567890}
\end{codeexample}

\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,
    precision=2,
    set thousands separator={.}}
\pgfmathprintnumber{1234567890}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,
    precision=2,
    set thousands separator={,}}
\pgfmathprintnumber{1234567890}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,
    precision=2,
    set thousands separator={{{,}}}}
\pgfmathprintnumber{1234567890}
\end{codeexample}
    %
    The last example employs commas and disables the default comma-spacing.

    Use |\pgfkeysgetvalue{/pgf/number format/set thousands separator}\value| to
    get the current separator into |\value|.
\end{key}

\begin{stylekey}{/pgf/number format/1000 sep=\marg{text}}
    Just another name for |set thousands separator|.
\end{stylekey}

\begin{key}{/pgf/number format/1000 sep in fractionals=\marg{boolean} (initially false)}
    Configures whether the fractional part should also be grouped into groups
    of three digits.

    The value |true| will active the |1000 sep| for both, integer and
    fractional parts. The value |false| will active |1000 sep| only for the
    integer part.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    precision=999,
    set thousands separator={\,},
    1000 sep in fractionals,
    }
\pgfmathprintnumber{1234.1234567}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,fixed zerofill,
    precision=9,
    set thousands separator={\,},
    1000 sep in fractionals,
    }
\pgfmathprintnumber{1234.1234567}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/min exponent for 1000 sep=\marg{number} (initially 0)}
    Defines the smallest exponent in scientific notation which is required to
    draw thousand separators. The exponent is the number of digits minus one,
    so $\meta{number}=4$ will use thousand separators starting with $1e4 =
    10000$.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    int detect,
    1000 sep={\,},
    min exponent for 1000 sep=0}
\pgfmathprintnumber{5000}; \pgfmathprintnumber{1000000}
\end{codeexample}

\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    int detect,
    1000 sep={\,},
    min exponent for 1000 sep=4}
\pgfmathprintnumber{1000}; \pgfmathprintnumber{5000}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    int detect,
    1000 sep={\,},
    min exponent for 1000 sep=4}
\pgfmathprintnumber{10000}; \pgfmathprintnumber{1000000}
\end{codeexample}
    %
    \noindent A value of |0| disables this feature (negative values are
    ignored).
\end{key}

\begin{key}{/pgf/number format/use period}
    A predefined style which installs periods ``\texttt{.}'' as decimal
    separators and commas ``\texttt{,}'' as thousands separators. This style is
    the default.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,precision=2,use period}
\pgfmathprintnumber{12.3456}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,precision=2,use period}
\pgfmathprintnumber{1234.56}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/use comma}
    A predefined style which installs commas ``\texttt{,}'' as decimal
    separators and periods ``\texttt{.}'' as thousands separators.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,precision=2,use comma}
\pgfmathprintnumber{12.3456}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,fixed,precision=2,use comma}
\pgfmathprintnumber{1234.56}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/skip 0.=\marg{boolean} (initially false)}
    Configures whether numbers like $0.1$ shall be typeset as $.1$ or not.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,precision=2,
    skip 0.}
\pgfmathprintnumber{0.56}
\end{codeexample}
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,
    fixed,
    fixed zerofill,precision=2,
    skip 0.=false}
\pgfmathprintnumber{0.56}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/showpos=\marg{boolean} (initially false)}
    Enables or disables the display of plus signs for non-negative numbers.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/showpos}
\pgfmathprintnumber{12.345}
\end{codeexample}

\begin{codeexample}[]
\pgfkeys{/pgf/number format/showpos=false}
\pgfmathprintnumber{12.345}
\end{codeexample}

\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,showpos,sci}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{stylekey}{/pgf/number format/print sign=\marg{boolean}}
    A style which is simply an alias for |showpos=|\marg{boolean}.
\end{stylekey}

\begin{key}{/pgf/number format/sci 10e}
    Uses $m \cdot 10^e$ for any number displayed in scientific format.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci 10e}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/sci 10\textasciicircum e}
    The same as `|sci 10e|'.
\end{key}

\begin{key}{/pgf/number format/sci e}
    Uses the `$1e{+}0$' format which is generated by common scientific tools
    for any number displayed in scientific format.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci e}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/sci E}
    The same with an uppercase `\texttt{E}'.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci E}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/sci subscript}
    Typesets the exponent as subscript for any number displayed in scientific
    format. This style requires very little space.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci subscript}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/sci superscript}
    Typesets the exponent as superscript for any number displayed in scientific
    format. This style requires very little space.
    %
\begin{codeexample}[]
\pgfkeys{/pgf/number format/.cd,sci,sci superscript}
\pgfmathprintnumber{12.345}
\end{codeexample}
    %
\end{key}

\begin{key}{/pgf/number format/sci generic=\marg{keys}}
    Allows to define an own number style for the scientific format. Here,
    \meta{keys} can be one of the following choices (omit the long key prefix):

    \begin{key}{/pgf/number format/sci generic/mantissa sep=\marg{text} (initially empty)}
        Provides the separator between a mantissa and the exponent. It might be
        |\cdot|, for example,
    \end{key}
    %
    \begin{key}{/pgf/number format/sci generic/exponent=\marg{text} (initially empty)}
        Provides text to format the exponent. The actual exponent is available
        as argument |#1| (see below).
    \end{key}
    %
\begin{codeexample}[]
\pgfkeys{
    /pgf/number format/.cd,
    sci,
    sci generic={mantissa sep=\times,exponent={10^{#1}}}}
\pgfmathprintnumber{12.345};
\pgfmathprintnumber{0.00012345}
\end{codeexample}
    %
    The \meta{keys} can depend on three parameters, namely on |#1| which is the
    exponent, |#2| containing the flags entity of the floating point number and
    |#3| is the (unprocessed and unformatted) mantissa.

    Note that |sci generic| is \emph{not} suitable to modify the appearance of
    fixed point numbers, nor can it be used to format the mantissa (which is
    typeset like fixed point numbers). Use |dec sep|, |1000 sep| and
    |print sign| to customize the mantissa.
\end{key}

\begin{key}{/pgf/number format/retain unit mantissa=\mchoice{true,false} (initially true)}
    Allows to omit a unit mantissa.
    %
\begin{codeexample}[]
\pgfkeys{
    /pgf/number format/.cd,
    sci, retain unit mantissa=false}
\pgfmathprintnumber{10.5};
\pgfmathprintnumber{10};
\pgfmathprintnumber{1010};
\pgfmathprintnumber[precision=1]{-1010};
\end{codeexample}
    %
    The feature is applied after rounding to the desired precision: if the
    remaining mantissa is equal to~$1$, it will be omitted. It applies to all
    styles involving the scientific format (including |std|).
\end{key}

\begin{key}{/pgf/number format/\protect\atmarktext dec sep mark=\marg{text}}
    Will be placed right before the place where a decimal separator belongs to.
    However, \marg{text} will be inserted even if there is no decimal
    separator. It is intended as place-holder for auxiliary routines to find
    alignment positions.

    This key should never be used to change the decimal separator!
    Use |dec sep| instead.
\end{key}

\begin{key}{/pgf/number format/\protect\atmarktext sci exponent mark=\marg{text}}
    Will be placed right before exponents in scientific notation. It is
    intended as place-holder for auxiliary routines to find alignment
    positions.

    This key should never be used to change the exponent!
\end{key}

\begin{key}{/pgf/number format/assume math mode=\marg{boolean} (default true)}
    Set this to |true| if you don't want any checks for math mode. The initial
    setting checks whether math mode is active using |\pgfutilensuremath| for
    each final number.

    Use |assume math mode=true| if you know that math mode is active. In that
    case, the final number is typeset as-is, no further checking is performed.
\end{key}

\begin{stylekey}{/pgf/number format/verbatim}
    A style which configures the number printer to produce verbatim text
    output, i.e., it doesn't contain \TeX\ macros.
    %
\begin{codeexample}[preamble={\usetikzlibrary{fpu}}]
\pgfkeys{
    /pgf/fpu,
    /pgf/number format/.cd,
    sci,
    verbatim}
\pgfmathprintnumber{12.345};
\pgfmathprintnumber{0.00012345};
\pgfmathparse{exp(15)}
\pgfmathprintnumber{\pgfmathresult}
\end{codeexample}
    %
    The style resets |1000 sep|, |dec sep|, |print sign|, |skip 0.| and sets
    |assume math mode|. Furthermore, it installs a |sci generic| format for
    verbatim output of scientific numbers.

    However, it will still respect |precision|, |fixed zerofill|,
    |sci zerofill| and the overall styles |fixed|, |sci|, |int detect| (and
    their variants). It might be useful if you intend to write output files.
\end{stylekey}


%--------------------------------------------------
% \subsubsection{Defining own display styles}
% You can define own display styles, although this may require some insight into \TeX-programming. Here are two examples:
% \begin{enumerate}
%     \item A new fixed point display style: The following code defines a new style named `\texttt{my own fixed point style}' which uses $1{\cdot}00$ instead of $1.00$.
% \begin{lstlisting}
% \def\myfixedpointstyleimpl#1.#2\relax{%
%     #1{\cdot}#2%
% }%
% \def\myfixedpointstyle#1{%
%     \pgfutilensuremath{%
%     \ifpgfmathfloatroundhasperiod
%         \expandafter\myfixedpointstyleimpl#1\relax
%     \else
%         #1%
%     \fi
%     }%
% }
% \pgfkeys{/my own fixed point style/.code={%
%     \let\pgfmathprintnumber@fixed@style=\myfixedpointstyle}
% }%
% \end{lstlisting}
%     You only need to overwrite the macro \lstinline!\pgfmathprintnumber@fixed@style!. This macro takes one argument (the result of any numerical computations). The \TeX-boolean \lstinline!\ifpgfmathfloatroundhasperiod! is true if and only if the input number contains a period.
%
%     \item An example for a new scientific display style:
% \begin{lstlisting}
% % #1:
% %         0 == '0' (the number is +- 0.0),
% %         1 == '+',
% %         2 == '-',
% %         3 == 'not a number'
% %         4 == '+ infinity'
% %         5 == '- infinity'
% % #2: the mantissa
% % #3: the exponent
% \def\myscistyle#1#2e#3\relax{%
%     ...
% }
% \pgfkeys{/my own sci style/.code={%
%     \let\pgfmathfloatrounddisplaystyle=\myscistyle},
% }%
% \end{lstlisting}
% \end{enumerate}
%--------------------------------------------------
