Histogram

Find the mean and standard deviation of a list of numbers.

Complete Code

POD for Macro Files

PG problem file

Explanation

DOCUMENT();

loadMacros(
    "PGstandard.pl",       "PGML.pl",
    'StatisticalPlots.pl', 'PGstatisticsmacros.pl',
    "PGcourse.pl"
);

Preamble

This produces a histogram using the StatisticalPlots.pl macro, which provides some convenience methods for creating Statistical plots. This also uses PGstatisticsmacros.pl to generate random values from the Normal distribution.

# of 9.  See PODLINK('PGstatisticsmacros.pl') for more information.

$dx   = 5;                               # bin size
@data = urand(30, 9, 50, 6);
$min  = floor(min(@data) / $dx) * $dx;
$max  = ceil(max(@data) / $dx) * $dx;

$histogramVertical = StatPlot(
    xmin            => $min - $dx / 2,
    xmax            => $max + $dx / 2,
    xtick_distance  => $dx,
    xminor          => 0,
    xmajor          => 0,
    xlabel          => '',
    xlocation       => 'bottom',
    ymin            => 0,
    ytick_distance  => 2,
    yminor          => 1,
    ylabel          => '',
    ylocation       => 'left',
    rounded_corners => 1
);
(undef, $vFrequencies) = $histogramVertical->add_histogram(
    ~~@data,
    min          => $min,
    max          => $max,
    bins         => ($max - $min) / $dx,
    fill_color   => 'blue',
    fill_opacity => 0.4,
    stroke_width => 1
);
$histogramVertical->axes->yaxis(max => max(@$vFrequencies) + 1);

# use the $vFrequencies to generate the alternative text.
$alt_text = 'A histogram with ' . scalar(@$vFrequencies) . ' bins.  ';
for my $i (1 .. scalar(@$vFrequencies)) {
    $alt_text .=
        "Bin $i is from "
        . ($min + ($i - 1) * $dx) . ' to '
        . ($min + $i * $dx)
        . ' and the height is '
        . $vFrequencies->[ $i - 1 ] . '.  ';
}

Setup

The urand function produces normally distributed random numbers. This will generate an array of 50 data values with a mean of 30 and standard deviation

To get nice bin sizes (in this case of width 5), the min and max are found and then are passed into the add_histogram method. The vertical maximum is calculated from the data and then the ymax is set with the ->axes->yaxis method.

See StatisticalPlots.pl for other options to this method.

Make sure that an alternate text is added to all graphs for accessibility. Be detailed.

BEGIN_PGML

>>[! [$alt_text] !]{$histogramVertical}{400}<<

END_PGML

Statement

In this case, only the histogram is plotted. Make sure to add the alt text.

BEGIN_PGML_SOLUTION
If a question was asked, provide a solution.
END_PGML_SOLUTION

ENDDOCUMENT();

Solution

A solution should be provided here.