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<?php
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/*
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PHPlot / contrib / prune_labels
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$Id: prune_labels.php 454 2009-12-09 03:45:55Z lbayuk $
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PHPlot contrib code - public domain - no copyright - use as you wish
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Reduce the number of data labels along the X axis, when the density is too
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high. This simply blanks out M-1 of every M labels in the data array.
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There are other ways to do this, but we need to keep the labels uniformly
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spaced. You select the target maximum label count (maxlabels), and you will
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get no more than maxlabels data labels.
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Arguments:
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$data - The PHPlot data array (reference variable)
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$maxlabels - The maximum number of data labels you are willing to have,
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Returns: Nothing
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Modifies the $data array in place to remove some of the labels.
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Notes:
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The data array and its rows must be 0-based integer indexed arrays.
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*/
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function prune_labels(&$data, $maxlabels)
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{
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# Do nothing if there are not already too many labels:
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if (($n = count($data)) <= $maxlabels) return;
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# Compute how many labels to erase. Keep 1 of every $m labels.
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$m = (int)ceil($n / $maxlabels);
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# Process the data array, zapping M-1 of every M labels:
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$k = 0;
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for ($i = 0; $i < $n; $i++) {
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if ($k > 0) $data[$i][0] = '';
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if (++$k >= $m) $k = 0;
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}
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}
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