This is an advanced example that uses a drawing callback to add annotations to a plot. More information on this topic can be found in Section 4.4.5, “Using Callbacks to Annotate Plots”, where this example is described in detail.
Example 5.22. Annotated Plot
<?php # PHPlot Example: Annotating a plot using callbacks # Note: This example is coded for PHPlot > 5.0.7 require_once 'phplot.php'; # Get the Sales data. In real life, this would most likely come from # a database or external file. For this example, we will use 'random' # data, but with a fixed seed for repeatable results. function get_data() { mt_srand(1); $data = array(); # Build an array with 12 arrays of (month_name, value): for ($month = 1; $month <= 12; $month++) $data[] = array(strftime('%b', mktime(12, 0, 0, $month, 1)), 5 + mt_rand(5, 40)); return $data; } # Find the best and worst sales data. # Gets the Y value (sales data) and X value. For PHPlot text-data data, # the X values are assigned as 0.5, 1.5, 2.5, etc. # The data array is in 'text-data' format: array of array(label, Y)... function get_best_worst($data, &$best_index, &$best_sales, &$worst_index, &$worst_sales) { $best_sales = NULL; $worst_sales = NULL; foreach ($data as $x => $point) { if (!isset($best_sales) || $point[1] > $best_sales) { $best_sales = $point[1]; $best_index = $x + 0.5; } if (!isset($worst_sales) || $point[1] < $worst_sales) { $worst_sales = $point[1]; $worst_index = $x + 0.5; } } } # Plot annotation callback. # The pass-through argument is the PHPlot object. function annotate_plot($img, $plot) { global $best_index, $best_sales, $worst_index, $worst_sales; # Allocate our own colors, rather than poking into the PHPlot object: $red = imagecolorresolve($img, 255, 0, 0); $green = imagecolorresolve($img, 0, 216, 0); # Get the pixel coordinates of the data points for the best and worst: list($best_x, $best_y) = $plot->GetDeviceXY($best_index, $best_sales); list($worst_x, $worst_y) = $plot->GetDeviceXY($worst_index, $worst_sales); # Draw ellipses centered on those two points: imageellipse($img, $best_x, $best_y, 50, 20, $green); imageellipse($img, $worst_x, $worst_y, 50, 20, $red); # Place some text above the points: $font = '3'; $fh = imagefontheight($font); $fw = imagefontwidth($font); imagestring($img, $font, $best_x-$fw*4, $best_y-$fh-10, 'Good Job!', $green); # We can also use the PHPlot internal function for text. # It does the center/bottom alignment calculations for us. # Specify the font argument as NULL or '' to use the generic one. $plot->DrawText('', 0, $worst_x, $worst_y-10, $red, 'Bad News!', 'center', 'bottom'); } # Begin main processing: # Fill the data array: $data = get_data(); # Find the best and worst months: get_best_worst($data, $best_index, $best_sales, $worst_index, $worst_sales); # Create the PHPlot object, set title, plot type, data array type, and data: $plot = new PHPlot(800, 600); $plot->SetTitle('Monthly Widget Sales'); $plot->SetPlotType('bars'); $plot->SetDataType('text-data'); $plot->SetDataValues($data); # Borders are needed for the manual: $plot->SetImageBorderType('plain'); # Select X data labels (not tick labels): $plot->SetXTickPos('none'); $plot->SetXTickLabelPos('none'); $plot->SetXDataLabelPos('plotdown'); # Format Y labels as "$nM" with no decimals, steps of 5: $plot->SetYLabelType('data', 0, '$', 'M'); $plot->SetYTickIncrement(5.0); # Force the bottom of the plot to be at Y=0, and omit # the bottom "$0M" tick label because it looks odd: $plot->SetPlotAreaWorld(NULL, 0); $plot->SetSkipBottomTick(True); # Establish the drawing callback to do the annotation: $plot->SetCallback('draw_all', 'annotate_plot', $plot); # Draw the graph: $plot->DrawGraph();
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