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phpjpgraph

Use multiple mark styles on one plot line with jpgraph

I have a set of data that spans a number of dates. Some of the data points need to be identified with a different style so they stand out. I can approximate what I need by creating 2 plot lines using different mark styles but it doesn't look cohesive and can be confusing to some people. Here is an example using that method.

Sample Graph with 2 plot lines

All of the data points in the sample above should be connected. The questions are

  • Is it possible to create a single plot line with different mark styles?
  • If the answer to the above is no is there a way to somehow "merge" the 2 plot lines so all of the points get connected?

The code that created the sample graph:

<?php
require_once 'jpgraph/jpgraph.php';
require_once 'jpgraph/jpgraph_line.php';
require_once 'jpgraph/jpgraph_date.php';

$line1D = array(1497844800,1498449600,1505102400,1516597200);
$line1Y = array(79.00,76.00,53.00,14.00);
$line2D = array(1504584000,1507521600);
$line2Y = array(9.87,9.93);

$graph = new Graph(640,480);
$graph->clearTheme();
$graph->SetScale('datlin');

$graph->xaxis->SetLabelAngle(60);
$graph->xaxis->SetFont(FF_ARIAL,FS_NORMAL,8);
$graph->xaxis->SetLabelFormatString('m/d/Y',true);
$graph->yaxis->scale->SetGrace(5);

$line1=new LinePlot($line1Y,$line1D);
$line1->SetColor('#4A6EC6');
$line1->SetWeight(2);
$line1->mark->SetFillColor('#4A6EC6');
$line1->mark->SetType(MARK_FILLEDCIRCLE);
$graph->Add($line1);

$line2=new LinePlot($line2Y,$line2D);
$line2->SetColor('#4A6EC6');
$line2->SetWeight(2);
$line2->mark->SetType(MARK_CIRCLE);
$line2->mark->SetColor('#4A6EC6');
$graph->Add($line2);

$graph->Stroke();  // display the graph
?>
Solution

  • The way to have different marks on a line is to create a 3rd line that is just the line without any marks. Then change the current lines that have marks to be scatter plots instead so just the points are added with the desired marks. When the 3 things are plotted together, 2 scatter plots and the line, they come together as a single line with different marks.

    The modified code that works as desired is:

    <?php
require_once 'jpgraph/jpgraph.php';
require_once 'jpgraph/jpgraph_line.php';
require_once 'jpgraph/jpgraph_date.php';
require_once 'jpgraph/jpgraph_scatter.php';

$line1D = array(1497844800,1498449600,1505102400,1516597200);
$line1Y = array(79.00,76.00,53.00,14.00);
$line2D = array(1504584000,1507521600);
$line2Y = array(9.87,9.93);

$line3D = array_merge($line1D,$line2D);
$line3Y = array_merge($line1Y,$line2Y);

$graph = new Graph(640,480);
$graph->clearTheme();
$graph->SetScale('datlin');

$graph->xaxis->SetLabelAngle(60);
$graph->xaxis->SetFont(FF_ARIAL,FS_NORMAL,8);
$graph->xaxis->SetLabelFormatString('m/d/Y',true);
$graph->yaxis->scale->SetGrace(5);

$line1=new ScatterPlot($line1Y,$line1D);
$line1->SetColor('#4A6EC6');
$line1->SetWeight(2);
$line1->mark->SetFillColor('#4A6EC6');
$line1->mark->SetType(MARK_FILLEDCIRCLE);
$graph->Add($line1);

$line2=new ScatterPlot($line2Y,$line2D);
$line2->SetColor('#4A6EC6');
$line2->SetWeight(2);
$line2->mark->SetType(MARK_CIRCLE);
$line2->mark->SetColor('#4A6EC6');
$graph->Add($line2);

$line3=new LinePlot($line3Y,$line3D);
$line3->SetColor('#4A6EC6');
$line3->SetWeight(2);
$graph->Add($line3);

$graph->Stroke();  // display the graph
?>