d3_selectionPrototype.attr = function(name, value) {

  name = d3.ns.qualify(name);

  // If no value is specified, return the first value.

  if (arguments.length < 2) {

    var node = this.node();

    return name.local

        ? node.getAttributeNS(name.space, name.local)

        : node.getAttribute(name);

  }

  function attrNull() {

    this.removeAttribute(name);

  }

  function attrNullNS() {

    this.removeAttributeNS(name.space, name.local);

  }

  function attrConstant() {

    this.setAttribute(name, value);

  }

  function attrConstantNS() {

    this.setAttributeNS(name.space, name.local, value);

  }

  function attrFunction() {

    var x = value.apply(this, arguments);

    if (x == null) this.removeAttribute(name);

    else this.setAttribute(name, x);

  }

  function attrFunctionNS() {

    var x = value.apply(this, arguments);

    if (x == null) this.removeAttributeNS(name.space, name.local);

    else this.setAttributeNS(name.space, name.local, x);

  }

  return this.each(value == null

      ? (name.local ? attrNullNS : attrNull) : (typeof value === "function"

      ? (name.local ? attrFunctionNS : attrFunction)

      : (name.local ? attrConstantNS : attrConstant)));

};