Scaling is one of the most important topics when it comes to chart your data. pChart can handle many way of tuning the scaling algorithm so you‘ll be able to represent accurately your data with the best visual & readable result. Today the scaling engine can accept many parameters to allow you to stay in full-automatic, assisted or completely manual mode.



By default the scaling engine is configured to automatically compute the scale based on the overall MIN and MAX values of all the drawable dataseries. A "margin" value is added to the MIN/MAX boundaries to avoid that the chart will go outside the drawing area boundaries. Automatic computing of the scale occurs with the following modes :



The example below shows what the automatic scale will produce with it‘s default configuration with a dataset of 24,-25,26,25,25 :

 /* pChart library inclusions */
 include("../class/pData.class.php");
 include("../class/pDraw.class.php");
 include("../class/pImage.class.php");

 /* Create and populate the pData object */
 $MyData = new pData();  
 $MyData->addPoints(array(24,-25,26,25,25),"Temperature");
 $MyData->setAxisName(0,"Temperatures");
 $MyData->addPoints(array("Jan","Feb","Mar","Apr","May","Jun"),"Labels");
 $MyData->setSerieDescription("Labels","Months");
 $MyData->setAbscissa("Labels");

 /* Create the pChart object */
 $myPicture = new pImage(700,230,$MyData);

 /* Add a border to the picture */
 $myPicture->drawRectangle(0,0,699,229,array("R"=>0,"G"=>0,"B"=>0));

 /* Set the default font */
 $myPicture->setFontProperties(array("FontName"=>"../fonts/pf_arma_five.ttf","FontSize"=>6));

 /* Define the chart area */
 $myPicture->setGraphArea(60,30,650,190);

 /* Draw the basic scale */
 $scaleSettings = array("GridR"=>200,"GridG"=>200,"GridB"=>200,"DrawSubTicks"=>TRUE,"CycleBackground"=>TRUE);
 $myPicture->drawScale($scaleSettings);

 /* Render the picture (choose the best way) */
 $myPicture->autoOutput("pictures/example.png");

In some cases, you may want to have the scale start to 0. As the automatic mode is computing the MIN value depending of your dataset and the margin option, you‘ll have to change the scaling mode to one of this two values :



The example below shows what the assisted scale will produce with a dataset of 24,4,26,25,25 :

 /* pChart library inclusions */
 include("../class/pData.class.php");
 include("../class/pDraw.class.php");
 include("../class/pImage.class.php");

 /* Create and populate the pData object */
 $MyData = new pData();  
 $MyData->addPoints(array(24,4,26,25,25),"Temperature");
 $MyData->setAxisName(0,"Temperatures");
 $MyData->addPoints(array("Jan","Feb","Mar","Apr","May","Jun"),"Labels");
 $MyData->setSerieDescription("Labels","Months");
 $MyData->setAbscissa("Labels");

 /* Create the pChart object */
 $myPicture = new pImage(700,230,$MyData);

 /* Add a border to the picture */
 $myPicture->drawRectangle(0,0,699,229,array("R"=>0,"G"=>0,"B"=>0));

 /* Set the default font */
 $myPicture->setFontProperties(array("FontName"=>"../fonts/pf_arma_five.ttf","FontSize"=>6));

 /* Define the chart area */
 $myPicture->setGraphArea(60,30,650,190);

 /* Draw the basic scale */
 $scaleSettings = array("GridR"=>200,"GridG"=>200,"GridB"=>200,"DrawSubTicks"=>TRUE,"CycleBackground"=>TRUE,"Mode"=>SCALE_MODE_START0);
 $myPicture->drawScale($scaleSettings);

 /* Render the picture (choose the best way) */
 $myPicture->autoOutput("pictures/example.a.scale.default.png");

You may want to configure a static scale. In this mode you‘ll have to provide the MIN and MAX values of each X-Axis. These values are provided through an array.



The example below shows what the manual scale will produce with fixed 0-100 boundaries. The dataset have no influence on the produced scale.

 /* pChart library inclusions */
 include("../class/pData.class.php");
 include("../class/pDraw.class.php");
 include("../class/pImage.class.php");

 /* Create and populate the pData object */
 $MyData = new pData();  
 $MyData->addPoints(array(24,4,26,25,25),"Temperature");
 $MyData->setAxisName(0,"Temperatures");
 $MyData->addPoints(array("Jan","Feb","Mar","Apr","May","Jun"),"Labels");
 $MyData->setSerieDescription("Labels","Months");
 $MyData->setAbscissa("Labels");

 /* Create the pChart object */
 $myPicture = new pImage(700,230,$MyData);

 /* Add a border to the picture */
 $myPicture->drawRectangle(0,0,699,229,array("R"=>0,"G"=>0,"B"=>0));

 /* Set the default font */
 $myPicture->setFontProperties(array("FontName"=>"../fonts/pf_arma_five.ttf","FontSize"=>6));

 /* Define the chart area */
 $myPicture->setGraphArea(60,30,650,190);

 /* Draw the basic scale */
 $AxisBoundaries = array(0=>array("Min"=>0,"Max"=>100));
 $scaleSettings  = array("GridR"=>200,"GridG"=>200,"GridB"=>200,"DrawSubTicks"=>TRUE,"CycleBackground"=>TRUE,"Mode"=>SCALE_MODE_MANUAL, "ManualScale"=>$AxisBoundaries);
 $myPicture->drawScale($scaleSettings);

 /* Render the picture (choose the best way) */
 $myPicture->autoOutput("pictures/example.a.scale.default.png");

The Manual scale array is formatted this way when using two axis (formerly 0 and 1) :

 $AxisBoundaries = array(0=>array("Min"=>0,"Max"=>100),1=>array("Min"=>10,"Max"=>20));

or also in a more readable way :

 $AxisBoundaries = "";
 $AxisBoundaries[0] = array("Min"=>0,"Max"=>100);
 $AxisBoundaries[1] = array("Min"=>10,"Max"=>20);