d3.js how to get minimum value of scale's domain when using nice()

Question

I have a scatter plot where I am trying to plot a reference point that should appear directly on the x-axis, but I am creating the y-axis like so:

   // give ourselves some space
    yMin = yMin * 0.9;
    yMax = yMax * 1.1;

    // set up y
    var yValue = function (d) {
            return d.price;
        },
        yScale = d3.scale.linear()
            .domain([yMin, yMax])
            .range([height, 0])
            .nice(),
        yAxis = d3.svg.axis()
            .scale(yScale)
            .orient("left");

The issue is that I want to plot a reference point directly on the x-axis. If I don't use .nice(), I can easily plot the reference point like so:

        var reference = svg.append('g').attr("class", "grid-reference");
        reference.append("circle").attr("id", "some-reference-value")
            .attr("class", "dot")
            .attr("r", 9)
            .attr("cx", xScale(someReferenceValue))
            .attr("cy", yScale(yMin))
            .style("fill", "grey")
            .style("opacity", 1);

but I can't seem to figure out how to do this when using .nice(). Is there another way I could go about this such as somehow getting the y-coordinate of the x-axis line?

I started digging through the d3 code to see how I could calculate the nice value and I understand the code, but it seems wasteful to calculate the value again not to mention the unnecessary maintenance of duplicate code - especially considering I also have reference points I will need to plot along the y-axis and I am using a logarithmic scale for my x-axis (the logarithmic nice() function is different from the linear nice() function so this would mean additional duplicate code and unnecessary maintenance).

Ideas?

Answer 1

You can simply query the scale for its domain after .nice() and then get the minimum value of that:

var yMin = yScale.domain()[0];