SVGGraph Bar Graphs

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• Stacked grouped bar graphs
• Histograms
• General options
• Grid-based graph options
• Bar graph options

SVGGraph currently contains these classes for drawing plain vertical bar graphs: BarGraph; StackedBarGraph; GroupedBarGraph; StackedGroupedBarGraph.

The Histogram class analyses the data values to draw a histogram.

Example code

Here are the settings and PHP code used to generate the graphs above:

<?php
require_once 'SVGGraph/autoloader.php';

$settings = array(
  'back_colour' => '#eee',
  'stroke_colour' => '#000',
  'back_stroke_width' => 0,
  'back_stroke_colour' => '#eee',
  'axis_colour' => '#333',
  'axis_overlap' => 2,
  'axis_font' => 'Arial',
  'axis_font_size' => 10,
  'grid_colour' => '#666',
  'label_colour' => '#000',
  'pad_right' => 20,
  'pad_left' => 20,
  'link_base' => '/',
  'link_target' => '_top',
  'minimum_grid_spacing' => 20
);

$values = array(
 array('Dough' => 30, 'Ray' => 50, 'Me' => 40, 'So' => 25, 'Far' => 45, 'Lard' => 35),
 array('Dough' => 20, 'Ray' => 30, 'Me' => 20, 'So' => 15, 'Far' => 25, 'Lard' => 35,
  'Tea' => 45)
);

$colours = array(
  array('red','yellow'), array('blue','white')
);
$links = array(
  'Dough' => 'jpegsaver.php', 'Ray' => 'crcdropper.php',
  'Me' => 'svggraph.php'
);

$graph = new Goat1000\SVGGraph\SVGGraph(300, 200, $settings);

$graph->colours($colours);
$graph->values($values);
$graph->links($links);
$graph->render('BarGraph');

This is not the actual code used - I have adapted it to make it easier to copy and paste it into a new file to try for yourself. To change the type of graph generated, change 'BarGraph' in the final call to $graph->render to one of the other types.

The StackedBarGraph example uses a different set of colours:

$colours = array(
 array('red','yellow','red','h'),
 array('blue','cyan','blue','h')
);

The final 'h' in the array of colours tells SVGGraph to create a horizontal gradient.

StackedGroupedBarGraph

The StackedGroupedBarGraph example adds two extra colours to those used by the BarGraph and GroupedBarGraph examples since it has four datasets to display:

$colours = array(
  array('red','yellow'),
  array('blue','white'), 
  array('green', 'pattern' => 'polkadot', 'size' => 6),
  array('orange','pattern' => 'check', 'size' => 6)
);

The StackedGroupedBarGraph must also be provided with the stack_group option to tell it where to break the stack into groups. The example graph above uses a value of “2” to show the 0th and 1st datasets in the first stack and the 2nd and 3rd datasets in the second stack. You can provide an array of values to display more than two stacks in each group. For this example with four datasets, setting stack_group to array(1, 2, 3) would put each of the datasets in its own stack, looking exactly like a GroupedBarGraph.

Histogram

The Histogram class works quite differently to the bar graph classes, even though it produces something that looks a lot like a bar graph. Instead of using each value in the data to calculate the height of a bar, it counts the occurrences of each value and groups them into ranges. The ranges of values are used for the X-axis, and the number of values in each range are used for the height of the bar.

The increment option allows you to choose the size of each data range on the X-axis. The default of NULL will let SVGGraph pick an increment that will give you a reasonable number of bars. The percentage option switches the Y-axis value from an absolute count to the percentage of all values.

Settings

These options are common to all graph types.

This table lists the options that are common to all the grid-based graph types - the options for grid spacing, axis labelling, etc.

The options in this table are for use with the bar graphs. Note: bar_label_* options have been superseded by data_label_* options in version 2.18. See the data labels page for details.

• ^[1]For GroupedBarGraph, bar_space is the space between groups of bars.
• ^[2]Bar label options have been replaced by global data_label_* options.
• ^[3]Only used for GroupedBarGraph.
• ^[4]Only used for StackedBarGraph and StackedGroupedBarGraph.
• ^[5]Added in version 2.18 to control new data_label-based labels. When not set, options for data labels are used.
• ^[6]Only used for StackedGroupedBarGraph.
• ^[7]Only used for Histogram.

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