D3.js复制我的数据

我正在尝试为一些与学生相关的数据创建数据可视化（下面的示例记录），但是当 d3 呈现它时，它会遍历数据两次并覆盖它，只在屏幕上留下第二次结果。我在这里使用行计数器，所以我有办法根据矩形的数量设置每个矩形的 y 坐标。我认为这在某种程度上把事情搞砸了。任何关于如何使数据不会迭代两次的帮助将不胜感激。

此外，为了以防万一，此代码位于一个角度.js指令中。

抱歉，如果我只是在这里做一些非常愚蠢的事情

// student records sample...
var studentData = [
{   
"studentID" : 1001,
"firstName" : "jill",
"lastName" : "smith",
"workLoadDifficulty" : 16,
"smileStartAngle" : -90,
"smileEndAngle" : 90,
},
{   
"studentID" : 1008,
"firstName" : "bob",
"lastName" : "smith",
"workLoadDifficulty" : 99,
"smileStartAngle" : 90,
"smileEndAngle" : -90,
}
];
(function () {
'use strict';
angular.module('learnerApp.directives')
.directive('d3Bars', ['d3', function(d3) {
  return {
    restrict: 'EA',
    scope: {
      data: "=",
      label: "@",
      onClick: "&"
    },
    link: function(scope, iElement, iAttrs) {
      var paddingForShape = 10;
      var rowCounter = -1;
      var height = 400;
      var width = 300;
      var svgContainer = d3.select(iElement[0])
          .append("svg")
          .attr("width", width)
          .attr('height', height);
      // on window resize, re-render d3 canvas
      window.onresize = function() {
        return scope.$apply();
      };
      scope.$watch(function(){
          return angular.element(window)[0].innerWidth;
        }, function(){
          return scope.render(scope.data);
        }
      );
      // watch for data changes and re-render
    scope.$watch('studentData', function(newVals, oldVals) {
        return scope.render(newVals);
      }, true); 
      // define render function
      scope.render = function(data){
        // remove all previous items before render
      svgContainer.selectAll("*").remove();
      var workLoadColor = d3.scale.category10()
            .domain([0,100])
            .range(['#02FA28', '#73FA87', '#C0FAC9','#FAE4C0', '#FAC775', '#FAA823','#FA9A00','#FA8288', '#FC4750', '#FA0511' ])

   var studentRects = svgContainer.selectAll('rect')
      .data(studentData, function(d) { 
        console.log(d.studentID);
        console.log('hello');
        return "keyVal" + d.studentID;
         })
      .enter()
        .append("rect");
      var studentRectAttributes = studentRects
                .attr("x", function(d,i) {
                    return ((i * 50) % width) + paddingForShape;
                })
                .attr("y", function(d,i) {
                    var value = ((i * 50) % width)
                    if (value === 0) {
                      rowCounter = rowCounter + 1;
                    }                    
                    var value = (rowCounter * 50);
                    console.log('Y Val: ', i);
                    console.log(value);
                    return value;
                })                   
                .attr("height", 30)
                .attr("width", 40)
                .style("fill", function(d) {
                  return workLoadColor(d.workLoadDifficulty)
                });

      };
    }
  };
}]);
}());