viewportMinimum: Number

Viewport is the visible range of the axis and viewportMinimum allows you to set its minimum value. This can be used in combination with viewportMaximum in order to zoom into a certain region programmatically.

• viewportMinimum and viewportMaximum are useful in setting the initial zoom in a chart.
• If viewportMinimum and viewportMaximum are not set, minimum and maximum values of axis will become the viewport’s range.
• Setting viewportMinimum or viewportMaximum will make the zoom/pan toolBar visible. Clicking the reset button will set the viewport range to viewportMinimum and viewportMaximum.
• Setting viewportMinimum and viewportMaximum of all axis to null will hide the toolBar – equivalent to clicking reset button.

var  chart =  new  CanvasJS.Chart("container",
{
 .
 .
 axisY:{
   viewportMinimum: -50,
   viewportMaximum: 50
 },
 .
 . 
});
chart.render();