 // get the current width of the div where the chart appear
  const width = parseInt( d3.select('#my_dataviz').style('width'), 10 )

  // Set the canvas height = height of the width
  const height = width/2
  ctx.height= height

console.log(width, height)
  // Set a projection for the map. Projection = transform a lat/long on a position on the 2d map.
  const projection = d3.geoMercator()
      .scale(35)
      .translate([150,100])

  // geographic path generator for given projection and canvas context
  c