How do I prevent graph elements from reaching the axis of my graph in D3 and scale properly?

Question

I have currently have a quick test for a graph I'm about to create for website and I have made the most basic functionality. I have a graph, a 4 elements and an x and a y axis and a zoom functionality.

My problem lies in the fact that when I zoom on the graph, the elements are able to reach the axis and overlap it. I've pasted my source code below

    //Setting generic width and height values for our SVG.
    var margin = {top: 60, right: 0, bottom: 60, left: 40},
        width = 1024 - 70 - margin.left - margin.right,
        height = 668 - margin.top - margin.bottom;

     //Other variable declarations.


    //Creating scales used to scale everything to the size of the SVG.
    var xScale = d3.scale.linear()
        .domain([0, 1024])
        .range([0, width]);

    var yScale = d3.scale.linear()
        .domain([1, 768])
        .range([height, 0]);

    //Creates an xAxis variable that can be used in our SVG.
    var xAxis = d3.svg.axis()
        .scale(xScale)
        .orient("bottom");

    var yAxis = d3.svg.axis()
        .scale(yScale)
        .orient("left");

    //Zoom command ...
    var zoom = d3.behavior.zoom()
        .x(xScale)
        .y(yScale)
        .scaleExtent([1, 10])
        .on("zoom", zoomTargets);


    // The mark '#' indicates an ID. IF '#' isn't included argument expected is a tag such as "svg" or "p" etc..
    var SVG = d3.select("#mainSVG")
                .attr("width", width + margin.left + margin.right)
                .attr("height", height + margin.top + margin.bottom)
                .append("g")
                .attr("transform", "translate(" + margin.left + "," + margin.top + ")")
                .call(zoom);


    //Create background. The mouse must be over an object on the graph for the zoom to work. The rectangle will cover the entire graph.
    var rect = SVG.append("rect")
        .attr("width", width)
        .attr("height", height);

    //Showing the axis that we created earlier in the script for both X and Y.
    var xAxisGroup = SVG.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

    var yAxisGroup = SVG.append("g")
        .attr("class", "y axis")
        .call(yAxis);

    //This selects 4 circles (non-existent, there requires data-binding) and appends them all below enter.
    //The amount of numbers in data is the amount of circles to be appended in the enter() section. 
    var circle = SVG
        .selectAll("circle")
        .data([40,100,400,1900])
        .enter()
            .append("circle")
            .attr("cx",function(d){return xScale(d)})
            .attr("cy",function(d){return yScale(d)})
            .attr("r",20);

    //Resets zoom when click on circle object. Zoom work now, should be changed to a button instead of click on circle though.
    SVG.selectAll("circle").on("click", function() {
        zoom.scale(1);
        zoom.translate([0,0]);
        zoomTargets();
    });

    function zoomTargets() {
       SVG.select(".x.axis").call(xAxis);
       SVG.select(".y.axis").call(yAxis);

       SVG.selectAll("circle").attr("cx",function(d){return xScale(d)}).attr("cy",function(d){return yScale(d)});
    }

    function resetZoom() {
        zoom.scale(1);
        zoom.translate([0,0]);
        zoomTargets();
    }

I've tried using "append("g2") before creating a circle to I can make g2 smaller than the entire svg, but that doesn't seem to work. As far as I have understood, you can just append a new element inside your existing one. I'm guessing I'm wrong since it hasn't worked for me.

Thank you in advance for your help.

Answer 1

Leave a small gap between the most extreme data point and the axis. In particular, you may want the range of your domain to take the margins into account:

var xScale = d3.scale.linear()
    .domain([0, 1024])
    .range([0, width-margin.right]);

var yScale = d3.scale.linear()
    .domain([1, 768])
    .range([height, margin.bottom]);