function render(svg) {
let selection = d3.select(svg);
let data = hexdataGroupped.get(currentTime)
selection.selectAll('circle')
.data(data)
.join('circle')
.attr('cx', d => proj([d.lng, d.lat])[0])
.attr('cy', d => proj([d.lng, d.lat])[1])
.attr('fill', d => colorPM1(d.pm1))
.attr('opacity', 0.5)
.attr('r', 2);
selection.selectAll('path')
.data(states.features)
.join('path')
.attr('d', f => path(f))
.attr('stroke', 'grey')
.attr('fill', 'none');
}