D3更新条形图

Question

So I'm relatively new to D3, but I have been trouble shooting this issue for a few days, with no luck. Wondering if I'm making a newbie mistake.

I'm attempting to create a graph which represents volume vs. time, and allow the user to update the graph with a different date range.

function updateVolumeGraph(data, div) {

//Get the data again
data.forEach(function(d) {
    d.startTime = new Date(d.startTime);
    d.totalVolume = d.totalVolume;
});

//Scale the range of the data again 
x.domain(d3.extent(data, function(d) { return d.startTime;}));
y.domain([0, d3.max(data, function(d) { return d.totalVolume; })]);

//Select the section we want to apply our changes to
var graphElement = d3.select(div).transition();

var bars = graphElement.selectAll(".bar").data(data); <<< Undefined

//Add some bars
bars.enter().append("rect")
             .attr("class", "bar")
              .attr("x", function(d) { return x(d.startTime); })
              .attr("y", function(d) { return y(d.totalVolume); })
              .attr("height", function(d) { return height - y(d.totalVolume); })
              .attr("width", barWidth);

    svg.select(".x.axis") // change the x axis
        .duration(750)
        .call(xAxisVolume);
    svg.select(".y.axis") // change the y axis
        .duration(750)
        .call(yAxisVolume);
};

My issue comes at the place where I have tagged it as "Undefined". graphElement.selectAll(".bars") returns an array of "rects" but the .data(data) call is undefined.

Any advice you could offer would be most appreciated!

Answer 1

The issue you are having is that you are setting graphElement to the return value of you call to the transition method.

var graphElement = d3.select(div).transition();

var bars = graphElement.selectAll(".bar").data(data);

Instead of chaining these methods, try calling it as a separate call after setting the graphElement variable.

var graphElement = d3.select(div);
graphElement.transition();
var bars = graphElement.selectAll(".bar").data(data);