d3js: Dynamically updating node objects - d3.js

Question

I'm creating a force graph with nodes representing political candidates as circles. Each circle's radius corresponds to the candidate's approval rating (a percentage). I have data over three years. It's coming from a .CSV file. I'm working in d3.js, and I'm still very new.
What I'm trying to do is dynamically update each node object such that the radius reflects the currently-selected year. Loading the graph works fine: the first year (2013) works. But, when I switch to 2012, the DOM elements don't change: they retain their 2013 values. Here are the relevant snips of code:
After opening the CSV call:
data.forEach(function(d) {
var node = {
id: d.id,
name: d.candidate,
value: (parseInt(d["y"+year])),
radius: (parseInt(d["y"+year], 10))*3,
party: d.cand_party,
sex: d.gender
};
nodes.push(node);
});
And here's the update I'd like to do:
d3.select(window).on("keydown", function() {
switch (d3.event.keyCode) {
case 37: year = Math.max(year0, year - 1); break;
case 39: year = Math.min(year1, year + 1); break;
}
update ();
});
function update() {
title.text(year);
circles.transition(1500)
.attr("r", function(d) { return d.radius; });
};
The update() function is working, in that my title is switching to 2012, as desired. However, when I check each node's DOM info, I see that radius and value retain their 2013 values (the circles aren't changing size).
Any advice appreciated, thanks.

Answer 1

Posted too soon! In line with what Lars commented, I found this worked:
data.forEach(function(d) {
var node = {
id: d.id,
name: d.candidate,
value: (parseInt(d["y"+year])),
radius2014: (parseInt(d.y2014, 10))*3,
radius2013: (parseInt(d.y2013, 10))*3,
radius2012: (parseInt(d.y2012, 10))*3,
party: d.cand_party,
sex: d.gender
};
nodes.push(node);
});
And then calling things like so:
function update() {
title.text(year);
circles.transition(1500)
.attr("r", function(d) { return d["radius"+year]; });
};