Why isn't D3 transition working

Question

I'm new to D3 and having trouble smoothly transitioning between two data sets. Here's a super simplified version of what I have currently:

var h = 500;
var w = 500;

var data = [
  10,
  15,
  12,
  9
]

var data_two = [
  6,
  15,
  20,
  19,
  11
]

var vis = d3.select('body')
  .append('svg')
  .attr({
    height: 500,
    width: 500
  })
  .append('g');

function buildChart(data) {
  var square = vis.selectAll('rect')
      .data(data, function(d) { return d }) 

  square
    .transition()
    .duration(1000)
    .attr({
      x : function(d, i) { return 0 }  
    })

  square
    .enter()
    .append('rect')
    .attr({
      height : function(d, i) { return 10 },
      y      : function(d, i) { return i * 15 },
      width  : function(d, i) { return d * 5 },
      x      : function(d, i) { return 0 }
    });

  square
    .exit()
    .remove();
 } 

buildChart(data);

setTimeout(function() {
  buildChart(data_two)
}, 1000)

jsfiddle: http://jsfiddle.net/ncakby1a/

My desired results are to have the bars smoothly animate to the new widths after a one second delay. Instead, they just jump to the new state and I'm not sure why. Thanks in advance!

Answer 1

You're buildChart function is always placing new bars, it's never updating the bars you placed with data according to the data in data_two . To fix this, first append the rectangles using data , then select them & apply the transition:

var h = 500;
var w = 500;

var data = [
  10,
  15,
  12,
  9,
  3
]

var data_two = [
  6,
  15,
  20,
  19,
  11
]

var vis = d3.select('body')
  .append('svg')
  .attr({
    height: 500,
    width: 500
  })
  .append('g');

vis.selectAll('rect')
    .data(data)
    .enter()
    .append('rect')
    .attr({
        x: function(d, i){ return 0;},
        y: function(d, i){ return i * 15;},
        height: function(d){ return 10;},
        width: function(d){ return d * 5;}
    })

vis.selectAll('rect')
  .data(data_two)
  .transition()
  .duration(1000)
  .delay(1000)
  .attr({
     x: function(d, i){ return 0;},
     y: function(d, i){ return i * 15;},
     height: function(d){ return 10;},
     width: function(d){ return d * 5;}
  });

Here's a working JSfiddle