How do I read and modify axes on an already-drawn Google chart?

Question

I have a page with several google charts on it, mostly combo charts and line charts. For instance:

chart = new google.visualization.LineChart(chartDiv);
         


        

Answer 1

According to the documentation getVAxisValue function has the following signature:

getVAxisValue(position, optional_axis_index)

Returns the logical vertical value at position, which is an offset from the chart container's top edge. Can be negative.

Example: chart.getChartLayoutInterface().getVAxisValue(300).

Call this after the chart is drawn.

Return Type: number

---

Since your goal is to read the maximum values off of the axes and then redraw the charts so that they all have the same maximum values on their axes, i would suggest the following solution

calculate min/max values of google.visualization.DataTable:

function calcMinMax(data, colIndex)
{
   var totalMin  = data.getValue(0,colIndex);
   var totalMax = data.getValue(0,colIndex);
   for(var i = 0; i < data.getNumberOfRows();i++){
        if ( data.getValue(i, colIndex) < totalMin  ) {
          totalMin  = data.getValue(i, colIndex);
        }          
        if ( data.getValue(i, colIndex) > totalMax ) {
          totalMax = data.getValue(i, colIndex);
        }
   }
   return {'min': totalMin, 'max': totalMax };
} 

and set viewWindow option:

var vAxisMinMax = calcMinMax(data,1); 
options.vAxis = {'viewWindow': {'min': vAxisMinMax.min, 'max': vAxisMinMax.max}};

Example

google.load('visualization', '1', { packages: ['corechart', 'line'] });
google.setOnLoadCallback(drawBasic);

function drawBasic() {

    var data = new google.visualization.DataTable();
    data.addColumn('number', 'X');
    data.addColumn('number', 'Dogs');

    data.addRows([
      [0, 5], [1, 10], [2, 23], [3, 17], [4, 18], [5, 9],
      [6, 11], [7, 27], [8, 33], [9, 40], [10, 32], [11, 35],
      [12, 30], [13, 40], [14, 42], [15, 47], [16, 44], [17, 48],
      [18, 52], [19, 54], [20, 42], [21, 55], [22, 56], [23, 57],
      [24, 60], [25, 50], [26, 52], [27, 51], [28, 49], [29, 53],
      [30, 55], [31, 60], [32, 61], [33, 59], [34, 62], [35, 65],
      [36, 62], [37, 58], [38, 55], [39, 61], [40, 64], [41, 65],
      [42, 63], [43, 66], [44, 67], [45, 69], [46, 69], [47, 70],
      [48, 72], [49, 68], [50, 66], [51, 65], [52, 67], [53, 70],
      [54, 71], [55, 72], [56, 73], [57, 75], [58, 70], [59, 68],
      [60, 64], [61, 60], [62, 65], [63, 67], [64, 68], [65, 69],
      [66, 70], [67, 72], [68, 75], [69, 80]
    ]);

    var options = {
        hAxis: {
            title: 'Time'
        },
        vAxis: {
            title: 'Popularity'
        }
    };

    var chart = new google.visualization.LineChart(document.getElementById('chart_div'));


    var vAxisMinMax = calcMinMax(data,1); 
    options.vAxis = {'viewWindow': {'min': vAxisMinMax.min, 'max': vAxisMinMax.max}};
   

    chart.draw(data, options);

    
}





function calcMinMax(data, colIndex)
{
   var totalMin  = data.getValue(0,colIndex);
   var totalMax = data.getValue(0,colIndex);
   for(var i = 0; i < data.getNumberOfRows();i++){
        if ( data.getValue(i, colIndex) < totalMin  ) {
          totalMin  = data.getValue(i, colIndex);
        }          
        if ( data.getValue(i, colIndex) > totalMax ) {
          totalMax = data.getValue(i, colIndex);
        }
   }
   return {'min': totalMin, 'max': totalMax };
}