Return data based on dropdown menu?

Question

I am building a basic scatter plot where I\'d like to highlight specific points in my plot based on a dropdown selection. My code looks like this:

fill_arr =         


        

Answer 1

Access it using this.selectedIndex:

d3.select('select')
    .on("change", function() {

    key = this.selectedIndex;

    d3.selectAll('circle')
        .transition()
        .duration(300)
        .ease("quad")
        .attr( 'r', 5)
        .attr('cx', function(d) {return d.x;})
        .attr('cy', function(d) {return d.y;})
        // if a data point is selected highlight other 
        // data points of the same color
        .style('fill', function(d, i) { 
            if (d.label == key) 
            {return fill_arr[key]}
            else {return "#ccc"}
        ;})
});