In Google chart some different chart type contains different format of data sets

Google Chart Tools is with their default setting and all customizations are optional. Every chart exposes a number of options that customize its look and feel. These options are expressed as name:value pairs in the options object.
eg:
visualization supports a colors option that lets you specify

"colors": ['#e0440e', '#e6693e', '#ec8f6e', '#f3b49f', '#f6c7b6']

Lets create function to pass those

1 AddNewOption = function (name,value) {
2     options = $scope.chart.options
3     $scope.chart.options[name] = value;
4 };

Now use this option to improve our scatter chart

1 AddNewOption('pointShape','square');
2 AddNewOption('pointSize',20);

Now we can do more play with Google chart options.

Crosshair Options

Crosshairs can appear on focus, selection, or both. They're available for scatter charts, line charts, area charts, and for the line and area portions of combo charts.

When you hover over the points with crosshair option you can see some helping axis for the point. 

Here is crosshair API for to play more.

• crosshair: { trigger: 'both' }
  display on both focus and selection


• crosshair: { trigger: 'focus' }
  display on focus only


• crosshair: { trigger: 'selection' }
  display on selection only


• crosshair: { orientation: 'both' }
  display both horizontal and vertical hairs