Histogram of discrete integer values

Question

As the title says, I would like to create a histogram from integer values. My MWE is:

\documentclass[border=5]{standalone}
\usepackage{pgfplots}
%Random data between 10 and 20 -- could also be between 100 and 200 or what ever
\begin{filecontents}{data.txt}
        18
        15
        18
        19
        14
        15
        12
        11
        18
        18
        12
        11
        17
\end{filecontents}
\begin{document}
    \begin{tikzpicture}
        \begin{axis}[
            axis lines=left,
            ymajorgrids=true,
            title={Histogram},
            xlabel=points,
            ylabel=headcount,
            ybar
            ]
        \addplot+ [hist] table[y index= 0]{data.txt};
        \end{axis}
    \end{tikzpicture}
\end{document}

The result is:

What i would like to get is (note: unfortunately, I have double-counted the values):

My problems are, the x-axis is not discrete, and that's why the labels are shifted. I would like to have space between the bars - also between y-axis and the first bar and at the end.

Some additional infos: I am using LaTeX. I have already tried to set the precision to 0 and using datatool to first count the frequencies and then draw a simple bar chart. I have struggled with various label and area styles, but couldn't achieve my goal.

Answer 1

You can use gnuplot to create the histogram data and then plot these data as a bar plot. To compile, you need gnuplot installed and compile with --shell-escape : What does --shell-escape do?

\begin{filecontents*}{data.txt}
18
15
18
19
14
15
12
11
18
18
12
11
17
\end{filecontents*}
\documentclass[tikz, border=1cm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
ybar,
xmin=10, xmax=20,
ymin=0,
xtick distance=1,
axis lines=left,
ymajorgrids=true,
title={Not a Histogram}, xlabel=points, ylabel=headcount,
]
\addplot+[raw gnuplot] gnuplot {
binwidth=1;
bin(x,bw)=bw*floor(x/bw);
plot "data.txt" using (bin($1,binwidth)):(1.0) smooth freq;
};
\end{axis}
\end{tikzpicture}
\end{document}

Answer 2

• We can prepare the data with Latex3 and a random selection.

  \intarray_new:Nn \g_HISTO_myarray_intarray {9}

to store number between 1 and 9 excluded(11, 12, ..., 19). We add 10 when writing to the file \jobname.data

• If we already have a file ready or if we want to manually modify the data, we can modify this file and comment \histo[20].

• with pgfplots

  bar width=0.5cm and enlarge x limits={auto},enlarge y limits={upper}, so as not to stick to the axes

the code

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.18}
\ExplSyntaxOn
%%%%%%%%%%%%%%%%%%%%%%%%%%%
\sys_gset_rand_seed:n {240210}
%%%%%%%%%%%%%%%%%%%%%%%%%%%
\int_new:N \l_HISTO_randominteger_int
\intarray_new:Nn \g_HISTO_myarray_intarray {9}
\iow_new:N \g_HISTO_iow
%
\tl_new:N \l_HISTO_table_tl
\NewDocumentCommand{\histo}{O{10}}% 10 by default
    {
        \__array_fillarray:n{#1}       
        \__array_table:       
    }
\cs_new_protected:Nn __array_fillarray:n
{
    \int_step_inline:nnn {1} {#1} 
            {
                \int_set:Nn \l_HISTO_randominteger_int {\int_rand:nn {1} {9}}
                \intarray_gset:Nnn \g_HISTO_myarray_intarray 
                    { \l_HISTO_randominteger_int } 
                    { 
                        \intarray_item:Nn \g_HISTO_myarray_intarray {\l_HISTO_randominteger_int} + 1
                    }
                %\int_use:N \l_HISTO_randominteger_int \quad % uncomment to see the numbers
            }
    %\intarray_log:N \g_HISTO_myarray_intarray% <-- to see the intarray in the log
}
\cs_new_protected:Nn __array_table:
    {
        \iow_open:Nn \g_HISTO_iow {\jobname.data}
        \int_step_inline:nnn {1} {9}
            {
                \tl_clear:N \l_HISTO_table_tl
                \tl_put_right:Nn \l_HISTO_table_tl {\int_eval:n {10+##1}}%<-- between 11 and 19
                \tl_put_right:Nn \l_HISTO_table_tl {~}
                \tl_put_right:Nn \l_HISTO_table_tl {
                \intarray_item:Nn \g_HISTO_myarray_intarray {##1}}

                \iow_now:Nx \g_HISTO_iow { \l_HISTO_table_tl }
            }
        \iow_close:N \g_HISTO_iow 
    }
\ExplSyntaxOff
\begin{document}
\histo[20]
\begin{tikzpicture}
    \begin{axis}[
        %width=8cm, height=8cm,
        axis lines=left,
        ybar,
        bar width=0.5cm,
        ymajorgrids=true,
        title={Histogram ?},%<-- ?
        %
        xlabel=points,
        ylabel=headcount,
        xticklabel style = {font=\small},
        xtick=data,
        enlarge x limits={auto},
        enlarge y limits={upper},
    ]
    \addplot table[y index=1]  {\jobname.data};
    \end{axis}
\end{tikzpicture}
\end{document}