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nbremer

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Brushable Horizontal Bar Chart - I

EDIT: I've now created a much more intuitive version of this chart. View version IV for a non-updating x axis and version V for a updating x axis. So you can basically ignore this one :)

For a bit more background, you can read my mini-blog about it Brushable & interactive bar chart in d3.js

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This brushable horizontal bar chart gives you the option to browse through a large dataset without the separate bars becoming too small.

You have the option to adjust how many bars you're seeing at the same time by adjusting the size of the little box on the right mini chart.

You can also move the box and see the bars that you've selected appear in a bigger form on the left. Moving can be done either by grabbing and moving the box or scrolling

I have another version that uses a slightly different way to transition can be found here: Brushable Horizontal Bar Chart - II

The reason why the code is divided up into the overarching functions is to prepare it a bit already for the charting framework that I work with at my day job (and yes, I know the global variables are not-done, but I'm not known for writing beautiful or short code :) )

Why the rainbow? Just because it made it more fun to look at during the development :) (Please don't use a rainbow for a serious case though)

Some options to think about: You can update the x axis domain to update when you select a new set of bars, so that the largest bar always fills the space. This way you can see the smaller bars with more detail. Just wondering if that is confusing for a viewer... which I finally did in Brushable Horizontal Bar Chart - III

Although I found tidbits to get to this point all over the web, the initial help to set up an ordinal brush came from this example

Tested in (new versions of) Chrome, Firefox and Safari

Built with blockbuilder.org

<!DOCTYPE html>
<head>
  <meta charset="utf-8">

<link href='https://fonts.googleapis.com/css?family=Open+Sans:300,400' rel='stylesheet' type='text/css'>

#title {
      font-size: 20px;
      padding-bottom: 10px;
      padding-top: 20px;
      font-weight: 300;
    }

#explanation {
      font-size: 12px;
      max-width: 620px;
      margin: 0 auto;
      padding-top: 10px;
      color: #ababab;
      font-weight: 300;
    }

.axis path,
    .axis line {
      fill: none;
    }

.y.axis path {
      display: none;
    }

.brush .extent {
      fill-opacity: .125;
      shape-rendering: crispEdges;
    }

.resize {
      display: inline !important; /* show when empty */
      fill: #7A7A7A;
      fill-opacity: 1;
      stroke: #7A7A7A;
      stroke-width: 2px;
    }

.bar {
      /*shape-rendering: crispEdges;*/
    }
  </style>

</head>

<body>

<div id="title">Brushable horizontal bar chart</div>
  <div id="chart"></div>
  <div id="explanation">You can see more or less of the total bar chart on the left by either dragging the box in the mini chart on the right or by scrolling your mouse. You can also click anywhere in the mini chart to center the box on that region. And you can increase and decrease the size of the box by dragging the top or bottom handle up or down.</div>

var data = [],
      svg,
      defs,
      gBrush,
      brush,
      main_xScale,
      mini_xScale,
      main_yScale,
      mini_yScale,
      main_yAxis,
      mini_width,
      brushTotalStart,
      brushTotalEnd,
      updatedData,
      mousewheelTimer,
      scrolling = false,
      scrollEnd = false;

init();

function init() {

//Create the random data
    for (var i = 0; i < 40; i++) {
      var my_object = {};
      my_object.key = i;
      my_object.country = makeWord();
      my_object.value = Math.floor(Math.random() * 600);
      data.push(my_object);
    }//for i 
    data.sort(function(a,b) { return b.value - a.value; });

/////////////////////////////////////////////////////////////
    ///////////////// Set-up SVG and wrappers ///////////////////
    /////////////////////////////////////////////////////////////

//Added only for the mouse wheel
    var zoomer = d3.behavior.zoom()
        .on("zoom", null);

var main_margin = {top: 10, right: 10, bottom: 10, left: 100},
        main_width = 500 - main_margin.left - main_margin.right,
        main_height = 400 - main_margin.top - main_margin.bottom;

var mini_margin = {top: 10, right: 10, bottom: 10, left: 10},
        mini_height = 400 - mini_margin.top - mini_margin.bottom;
    mini_width = 100 - mini_margin.left - mini_margin.right;

svg = d3.select("#chart").append("svg")
        .attr("class", "svgWrapper")
        .attr("width", main_width + main_margin.left + main_margin.right + mini_width + mini_margin.left + mini_margin.right)
        .attr("height", main_height + main_margin.top + main_margin.bottom)
        .call(zoomer)
        .on("wheel.zoom", scroll)
        //.on("mousewheel.zoom", scroll)
        //.on("DOMMouseScroll.zoom", scroll)
        //.on("MozMousePixelScroll.zoom", scroll)
        //Is this needed?
        .on("mousedown.zoom", null)
        .on("touchstart.zoom", null)
        .on("touchmove.zoom", null)
        .on("touchend.zoom", null);

var mainGroup = svg.append("g")
            .attr("class","mainGroup")
            .attr("transform","translate(" + main_margin.left + "," + main_margin.top + ")");

var miniGroup = svg.append("g")
            .attr("class","miniGroup")
            .attr("transform","translate(" + (main_margin.left + main_width + main_margin.right + mini_margin.left) + "," + mini_margin.top + ")");

var brushGroup = svg.append("g")
            .attr("class","brushGroup")
            .attr("transform","translate(" + (main_margin.left + main_width + main_margin.right + mini_margin.left) + "," + mini_margin.top + ")");

/////////////////////////////////////////////////////////////
    ////////////////////// Initiate scales //////////////////////
    /////////////////////////////////////////////////////////////

main_xScale = d3.scale.linear().range([0, main_width]);
    mini_xScale = d3.scale.linear().range([0, mini_width]);

main_yScale = d3.scale.ordinal().rangeRoundBands([0, main_height], 0.4, 0);
    mini_yScale = d3.scale.ordinal().rangeBands([0, mini_height], 0.4, 0);

//Create y axis object
    main_yAxis = d3.svg.axis()
      .scale(main_yScale)
      .orient("left")
      .tickSize(0)
      .outerTickSize(0);

//Add group for the y axis
    mainGroup.append("g")
        .attr("class", "y axis")
        .attr("transform", "translate(-5,0)");
 
    /////////////////////////////////////////////////////////////
    /////////////////////// Update scales ///////////////////////
    /////////////////////////////////////////////////////////////

//Update the scales
    main_xScale.domain([0, d3.max(data, function(d) { return d.value; })]);
    mini_xScale.domain([0, d3.max(data, function(d) { return d.value; })]);
    main_yScale.domain(data.map(function(d) { return d.country; }));
    mini_yScale.domain(data.map(function(d) { return d.country; }));

//Create the visual part of the y axis
    d3.select(".mainGroup").select(".y.axis").call(main_yAxis);

brushTotalStart = mini_yScale.domain()[0];
    brushTotalEnd = mini_yScale.domain()[1];

/////////////////////////////////////////////////////////////
    ///////////////////////// Create brush //////////////////////
    /////////////////////////////////////////////////////////////

//What should the first extent of the brush become - a bit arbitrary this
    var brushExtent = Math.max( 1, Math.min( 20, Math.round(data.length*0.2) ) );

brush = d3.svg.brush()
        .y(mini_yScale)
        .extent([mini_yScale(data[0].country), mini_yScale(data[brushExtent].country)])
        .on("brush", brushmove)
        .on("brushend", brushend);

//Set up the visual part of the brush
    gBrush = d3.select(".brushGroup").append("g")
      .attr("class", "brush")
      .call(brush);
    
    gBrush.selectAll(".resize")
      .append("line")
      .attr("x2", mini_width);

gBrush.selectAll(".resize")
      .append("path")
      .attr("d", d3.svg.symbol().type("triangle-up").size(20))
      .attr("transform", function(d,i) { 
        return i ? "translate(" + (mini_width/2) + "," + 4 + ") rotate(180)" : "translate(" + (mini_width/2) + "," + -4 + ") rotate(0)"; 
      });

gBrush.selectAll("rect")
      .attr("width", mini_width);

gBrush.select(".background")
      .on("mousedown.brush", brushcenter)
      .on("touchstart.brush", brushcenter);

///////////////////////////////////////////////////////////////////////////
    /////////////////// Create a rainbow gradient - for fun ///////////////////
    ///////////////////////////////////////////////////////////////////////////

defs = svg.append("defs")

//Create two separate gradients for the main and mini bar - just because it looks fun
    createGradient("gradient-rainbow-main", "60%");
    createGradient("gradient-rainbow-mini", "13%");

/////////////////////////////////////////////////////////////
    //////////////// Set-up the main bar chart //////////////////
    /////////////////////////////////////////////////////////////

//DATA JOIN
    var bar = d3.select(".mainGroup").selectAll(".bar")
        .data(data, function(d) { return d.key; });

//UPDATE
    bar
      .attr("width", function(d) { return main_xScale(d.value); })
      .attr("y", function(d,i) { return main_yScale(d.country); })
      .attr("height", main_yScale.rangeBand());

//ENTER
    bar.enter().append("rect")
      .attr("class", "bar")
      .attr("x", 0)
      .attr("width", function(d) { return main_xScale(d.value); })
      .attr("y", function(d,i) { return main_yScale(d.country); })
      .attr("height", main_yScale.rangeBand())
      .style("fill", "url(#gradient-rainbow-main)");
      //.style("fill", "#3B8C3D");

//EXIT
    bar.exit()
      .remove();

/////////////////////////////////////////////////////////////
    /////////////// Set-up the mini bar chart ///////////////////
    /////////////////////////////////////////////////////////////

//The mini brushable bar
    //DATA JOIN
    var mini_bar = d3.select(".miniGroup").selectAll(".bar")
      .data(data, function(d) { return d.key; });

//UDPATE
    mini_bar
      .attr("width", function(d) { return mini_xScale(d.value); })
      .attr("y", function(d,i) { return mini_yScale(d.country); })
      .attr("height", mini_yScale.rangeBand());

//ENTER
    mini_bar.enter().append("rect")
      .attr("class", "bar")
      .attr("x", 0)
      .attr("width", function(d) { return mini_xScale(d.value); })
      .attr("y", function(d,i) { return mini_yScale(d.country); })
      .attr("height", mini_yScale.rangeBand())
      .style("fill", "url(#gradient-rainbow-mini)");
      //.style("fill", "#3B8C3D");

//EXIT
    mini_bar.exit()
      .remove();

//Start the brush
    gBrush.call(brush.event);

}//init

//Function runs on a brush move - to update the big bar chart
  function update(data) {

//The transition (& delay) time of the bars and the axis
    var transTime = 400;
    var delayTime = scrollEnd ? 0 : transTime;

/////////////////////////////////////////////////////////////
    ///////////////////// Update the axis ///////////////////////
    /////////////////////////////////////////////////////////////

//Update the domain of the y scale of the big bar chart
    main_yScale.domain(data.map(function(d) { return d.country; }));

//Update the y axis of the big chart
    d3.select(".mainGroup")
      .select(".y.axis")
      .transition()
      .duration(transTime).delay(delayTime)
      .call(main_yAxis);

/////////////////////////////////////////////////////////////
    ////////// Update the bars of the main bar chart ////////////
    /////////////////////////////////////////////////////////////

//DATA JOIN
    var bar = d3.select(".mainGroup").selectAll(".bar")
        .data(data, function(d) { return d.key; });

//UPDATE
    bar
      .transition().duration(transTime).delay(delayTime)
      .attr("x", 0)
      .attr("width", function(d) { return main_xScale(d.value); })
      .attr("y", function(d,i) { return main_yScale(d.country); })
      .attr("height", main_yScale.rangeBand());

//ENTER
    bar.enter().append("rect")
      .attr("class", "bar")
      .attr("x", 0)
      .attr("width", 0)
      .attr("y", function(d,i) { return main_yScale(d.country); })
      .attr("height", main_yScale.rangeBand())
      .style("fill", "url(#gradient-rainbow-main)")
      .transition().duration(transTime).delay(delayTime*2)
      .attr("width", function(d) { return main_xScale(d.value); });

//EXIT
    bar.exit()
      .transition().duration(transTime)
      .attr("width", 0)
      .remove();

}//update

/////////////////////////////////////////////////////////////
  ////////////////////// Brush functions //////////////////////
  /////////////////////////////////////////////////////////////

//First function that runs on a brush move
  function brushmove() {
    
    //What is the extent of the brush
    var extent = brush.extent();

//Adjust the extent of the brush so that is snaps to the bars
    if (d3.event.mode === "move" || scrollEnd === true) {
      //If dragging, preserve the width of the extent

//Does the top edge lie closer to the upper or lower bar
      var topExtent = extent[0];
      //Using ES5 - https://stackoverflow.com/questions/8584902/get-closest-number-out-of-array
      var closestTop = mini_yScale.range().reduce(function (prev, curr) {
        return (Math.abs(curr - topExtent) < Math.abs(prev - topExtent) ? curr : prev);
      });

//Pixel location of the bottom bar
      var maxBar = d3.max(mini_yScale.range());
      //Does the top edge lie closer to the upper or lower bar
      var bottomExtent = extent[1];
      //Using ES5 - https://stackoverflow.com/questions/8584902/get-closest-number-out-of-array
      var closestBottom = mini_yScale.range().reduce(function (prev, curr) {
        return (Math.abs(curr - bottomExtent) < Math.abs(prev - bottomExtent) ? curr : prev);
      });

//Don't let it go over the last bar in the design
      if(maxBar === closestBottom) {
        //The new extent that snaps to the bars
        extent = [closestBottom+mini_yScale.rangeBand()-(extent[1] - extent[0]),closestBottom+mini_yScale.rangeBand()];
      } else {
        //The new extent that snaps to the bars
        extent = [closestTop,closestTop+(extent[1] - extent[0])];
      }//else

} else if (!scrolling) {
      //If changing size, snap to the nearest rect

//Find the pixel values of the bars that lie within the selected brush
      var pixelRanges = mini_yScale.range()
        .filter(function(d) { return (d >= extent[0]-mini_yScale.rangeBand()/2) && (d <= extent[1]); });

//The new extent that snaps to the bars within the selection
      extent = [d3.min(pixelRanges),d3.max(pixelRanges)+mini_yScale.rangeBand()];
    }//else if 
    //else do nothing - then it comes from the scrolling and the extent has already been determined

//Snap to rect edge - the new extent
    d3.select("g.brush")
      .call(brush.extent(extent));

//What bars are captured in the brush
    //During scrolling take a wider range and don't snap
    if( scrolling ) {
      var selected = mini_yScale.domain()
        .filter(function(d) { return (extent[0]-1e-3-mini_yScale.rangeBand() <= mini_yScale(d)) && (mini_yScale(d) <= extent[1]+1e-3+mini_yScale.rangeBand() ); }); 
    } else {
      var selected = mini_yScale.domain()
        .filter(function(d) { return (extent[0]-1e-3 <= mini_yScale(d)) && (mini_yScale(d) <= extent[1]+1e-3); }); 
    }

//Take a subset of the selected data from the original dataset
    updatedData = data.filter(function(d) { return selected.indexOf(d.country) > -1; });

//Update the colors of the mini chart - Make everything outside the brush grey
    d3.select(".miniGroup").selectAll(".bar")
      .style("fill", function(d, i) { return selected.indexOf(d.country) > -1 ? "url(#gradient-rainbow-mini)" : "#e0e0e0"; });
 
    ////Update the main chart
    ////If you want to see update during a brush moving uncomment this
    ////But that doesn't work very well with the transitions of the bars in the update function & scrolling
    //update(updatedData);

}//brushmove

//Finally update the data
  function brushend() {
    if(!scrolling) update(updatedData);
  }

//Based on https://bl.ocks.org/mbostock/6498000
  //What to do when the user clicks on another location along the brushable bar chart
  function brushcenter() {
    var target = d3.event.target,
        extent = brush.extent(),
        size = extent[1] - extent[0],
        range = mini_yScale.range(),
        y0 = d3.min(range) + size / 2,
        y1 = d3.max(range) + mini_yScale.rangeBand() - size / 2,
        center = Math.max( y0, Math.min( y1, d3.mouse(target)[1] ) );

d3.event.stopPropagation();

gBrush
        .call(brush.extent([center - size / 2, center + size / 2]))
        .call(brush.event);

}//brushcenter

/////////////////////////////////////////////////////////////
  ///////////////////// Scroll functions //////////////////////
  /////////////////////////////////////////////////////////////

//Function to calculate what should happen on a mouse scroll
  function scroll() {

if (mousewheelTimer) clearTimeout(mousewheelTimer);

var extent = brush.extent(),
      size = extent[1] - extent[0],
      range = mini_yScale.range(),
      y0 = d3.min(range),
      y1 = d3.max(range),
      dy = d3.event.deltaY,
      topSection;

scrolling = true;

if( extent[0] - dy < y0 ) {
      topSection = y0;
    } else if ( extent[1] - dy > y1 ) {
      topSection = y1 - size;
    } else {
      topSection = extent[0] - dy;
    }//else

//Once the person stops scrolling, run the update data function
    mousewheelTimer = setTimeout(function() {
        mousewheelTimer = null;
        scrolling = false;
        scrollEnd = true;

//Finally snap the brush and update the data
        gBrush
          .call(brush.event);

scrollEnd = false;
      }, 200);

d3.event.stopPropagation();
    d3.event.preventDefault();

//Update the brush position during the scrolling
    if(scrolling) {
      gBrush
          .call(brush.extent([ topSection, topSection + size ]))
          .call(brush.event);
    }//if

}//scroll

/////////////////////////////////////////////////////////////
  ///////////////////// Helper functions //////////////////////
  /////////////////////////////////////////////////////////////

//Create a gradient 
  function createGradient(idName, endPerc) {

var coloursRainbow = ["#EFB605", "#E9A501", "#E48405", "#E34914", "#DE0D2B", "#CF003E", "#B90050", "#A30F65", "#8E297E", "#724097", "#4F54A8", "#296DA4", "#0C8B8C", "#0DA471", "#39B15E", "#7EB852"];

defs.append("linearGradient")
      .attr("id", idName)
      .attr("gradientUnits", "userSpaceOnUse")
      .attr("x1", "0%").attr("y1", "0%")
      .attr("x2", endPerc).attr("y2", "0%")
      .selectAll("stop") 
      .data(coloursRainbow)                  
      .enter().append("stop") 
      .attr("offset", function(d,i) { return i/(coloursRainbow.length-1); })   
      .attr("stop-color", function(d) { return d; });
  }//createGradient

//Function to generate random strings of 5 letters - for the demo only
  function makeWord() {
      var possible_UC = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
      var text = possible_UC.charAt(Math.floor(Math.random() * possible_UC.length));
      
      var possible_LC = "abcdefghijklmnopqrstuvwxyz";

for( var i=0; i < 5; i++ )
          text += possible_LC.charAt(Math.floor(Math.random() * possible_LC.length));

return text;
  }//makeWord

</script>

</body>
</html>

https://d3js.org/d3.v3.min.js