D3 axis not getting updated

Question

I just got to know D3 and was trying some graphs using it. I have a bar chart, the x axis is ordinal and the y axis is quantitative. On calling update_bar_chart, I want the x and y axis and the bars to be updated accordingly. However, although the bars are getting updated , the x and y axis are not.

Here is the code:

function dbc_update_bar_chart(metric,sc) {
        data.length = 0;
        url = 'DBFetch.php/dbc_bar_chart/:'+metric+'/:'+sc
                    $.ajax({
                                    type:   'get',
                                    url:    url,
                                    success: function(jdata, status, jqXHR) {
                                        data = JSON.parse(jdata)
                                        //console.log(data)
                                        bar_chart.setSeries(data)
                                        bar_chart.x(d3.scale.ordinal().rangeRoundBands([0, (width - margins.left - margins.right)]).domain(data.map(function(d) {return d[0];})))
                                                   .y(d3.scale.linear().range([(height - margins.top - margins.bottom), 0]).domain([0,d3.max(data, function(d) {return d[1]; })]));                             
                                        renderAxes(_svg);
                                    }
                    })
}

    function renderAxes(svg) {
        xAxis = d3.svg.axis()
                            .scale(_x)
                            .orient("bottom");

        yAxis = d3.svg.axis()
                            .scale(_y)
                            .orient("left");
        if (!axesG) {
            console.log("Entered init axes")
            axesG = svg.append("g")
                    .attr("class", "bar_axes");

            axesG.append("g")
                    .attr("class", "bar_xaxis")
                    .attr("transform", function () {
                        return "translate(" + xStart() + "," + yStart() + ")";
                    })
                    .call(xAxis);

            axesG.append("g")
                    .attr("class", "bar_yaxis")
                    .attr("transform", function () {
                        return "translate(" + xStart() + "," + yEnd() + ")";
                    })
                    .call(yAxis);
        }
        else{
            console.log("Entered update axes")
            svg.selectAll(".bar_axes bar_xaxis").transition()
                .duration(750)
                .call(xAxis);

            console.log("updated x-axes")
            svg.selectAll(".bar_axes bar_yaxis").transition()
                    .duration(750)
                    .call(yAxis);
            console.log("updated y-axes")        
        }
    }

Answer 1

Your selectors for the existing axes are wrong. If you want to specify parent and child elements explicitly, they should be

svg.selectAll(".bar_axes > .bar_xaxis")
svg.selectAll(".bar_axes > .bar_yaxis")

However, you can also select the elements directly:

svg.selectAll(".bar_xaxis")
svg.selectAll(".bar_yaxis")