Using Protovis with Dynamically Loaded Data via JQuery
I am dynamically loading some social network data into a web page that I want to visualise using protovis.(Actually, the data is loaded in in a two pass process - first a list of user names is grabbed from Twitter, then a list of social connections is grabbed from the Google Social API.) The protovis code seems to run inside an event loop, which means the data loading code needs to be outside this loop.
How do I load the data into the page and parse it, before "switching on" the protovis event loop? At the moment, I think there's a race condition whereby protovis tries to visualise network data that hasn't been loaded and parsed yet?
<html><head><title></title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.2.6/jquery.min.js"></script>
<script type="text/javascript" src="../protovis-3.2/protovis-r3.2.js"></script>
<script type="text/javascript">
//getNet is where we get a list of Twitter usernames
function getNet(){
url="http://search.twitter.com/search.json?q=jisc11&callback=?"
$.getJSON(url,function(json){
users=[]
uniqusers={}
for (var u in json['results']) {
uniqusers[json['results'][u]['from_user']]=1
}
for (var uu in uniqusers)
users.push(uu)
getConnections(users)
})
}
//getConnections is where we find the connections between the users identified by the list of Twitter usernames
function getConnections(users){
//Google social API limits lookup to 50 URLs; need to page开发者_开发百科 this...
if (users.length>50)
users=users.slice(0,49)
str=''
for (var uic=0; uic<users.length; uic++)
str+='http://twitter.com/'+users[uic]+','
url='http://socialgraph.apis.google.com/lookup?q='+str+'&edo=1&callback=?';
$.getJSON(url,function(json){
graph={}
graph['nodes']=[]
userLoc={}
for (var uic=0; uic<users.length; uic++){
graph['nodes'].push({nodeName:users[uic]})
userLoc[users[uic]]=uic
}
graph['links']=[]
for (u in json['nodes']) {
name=u.replace('http://twitter.com/','')
for (var i in json['nodes'][u]['nodes_referenced']){
si=i.replace('http://twitter.com/','')
if ( si in userLoc ){
if (json['nodes'][u]['nodes_referenced'][i]['types'][0]=='contact')
graph['links'].push({source:userLoc[name], target:userLoc[si]})
}
}
}
followers={}
followers={nodes:graph['nodes'],links:graph['links']}
});
}
$(document).ready(function() {
users=['psychemedia','mweller','mhawksey','garethm','gconole','ambrouk']
//getConnections(users)
getNet()
})
</script>
</head>
<body>
<div id="center"><div id="fig">
<script type="text/javascript+protovis">
// This code is taken directly from the protovis example
var w = document.body.clientWidth,
h = document.body.clientHeight,
colors = pv.Colors.category19();
var vis = new pv.Panel()
.width(w)
.height(h)
.fillStyle("white")
.event("mousedown", pv.Behavior.pan())
.event("mousewheel", pv.Behavior.zoom());
var force = vis.add(pv.Layout.Force)
.nodes(followers.nodes)
.links(followers.links);
force.link.add(pv.Line);
force.node.add(pv.Dot)
.size(function(d) (d.linkDegree + 4) * Math.pow(this.scale, -1.5))
.fillStyle(function(d) d.fix ? "brown" : colors(d.group))
.strokeStyle(function() this.fillStyle().darker())
.lineWidth(1)
.title(function(d) d.nodeName)
.event("mousedown", pv.Behavior.drag())
.event("drag", force)
//comment out the next line to remove labels
//.anchor("center").add(pv.Label).textAlign("center").text(function(n) n.nodeName)
vis.render();
</script>
</div></div>
</body></html>
vis.render() is currently being called before you get the data. There may be other issues too, but it needs to be after getNet().
EDIT 1:
vis.render() is now after getNet(). I've put the protovis force layout creation code inside a function so that I can control when it executes, and made the vis and followers variables visible to both the initialization code and the createLayout code.
Protovis, particularly the force layout, is very unforgiving about errors - e.g. wrong structure or count of elements for nodes/links datastructure, and does not tell you what is going on, so in developing it is best to first use static data that you know is of the right kind, and then later replace with dynamically created data.
One part of the problem you were having is that using type="text/javascript+protovis"
invokes javascript rewriting by protovis. The code below uses type="text/javascript" and has the extra {}s and returns that using +protovis saves. This allows getJSON() and protovis to coexist in Chrome browser, without getNet() being called repeatedly.
<html><head><title></title>
<script type="text/javascript" src="jquery.js"></script>
<script type="text/javascript" src="protovis-d3.2.js"></script>
<body>
<div id="center"><div id="fig">
<script type="text/javascript">
var vis;
var followers={};
function createLayout(){
var w = document.body.clientWidth,
h = document.body.clientHeight,
colors = pv.Colors.category19();
vis = new pv.Panel()
.width(w)
.height(h)
.fillStyle("white")
.event("mousedown", pv.Behavior.pan())
.event("mousewheel", pv.Behavior.zoom());
var force = vis.add(pv.Layout.Force)
.nodes(followers.nodes)
.links(followers.links);
force.link.add(pv.Line);
force.node.add(pv.Dot)
.size(function(d){ return (d.linkDegree + 4) * Math.pow(this.scale, -1.5);})
.fillStyle(function(d){ return d.fix ? "brown" : colors(d.group);})
.strokeStyle(function(){ return this.fillStyle().darker();})
.lineWidth(1)
.title(function(d){return d.nodeName;})
.event("mousedown", pv.Behavior.drag())
.event("drag", force);
//comment out the next line to remove labels
//.anchor("center").add(pv.Label).textAlign("center").text(function(n) n.nodeName)
vis.render();
}
function getNet(){
// OK to have a getJSON function here.
followers={nodes:[{nodeName:'mweller', group:6},
{nodeName:'mhawksey', group:6},
{nodeName:'garethm', group:6},
{nodeName:'gconole', group:6},
{nodeName:'ambrouk', group:6}
],
links:[
{source:0, target:1, value:1},
{source:1, target:2, value:1},
{source:1, target:4, value:1},
{source:2, target:3, value:1},
{source:2, target:4, value:1},
{source:3, target:4, value:1}]};
}
$(document).ready(function() {
getNet();
createLayout();
})
</script>
</head>
</div></div>
</body></html>
EDIT 2:
In case you are interested in digging a bit deeper, the problem comes from this code in protovis:
pv.listen(window, "load", function() {
pv.$ = {i:0, x:document.getElementsByTagName("script")};
for (; pv.$.i < pv.$.x.length; pv.$.i++) {
pv.$.s = pv.$.x[pv.$.i];
if (pv.$.s.type == "text/javascript+protovis") {
try {
window.eval(pv.parse(pv.$.s.text));
} catch (e) {
pv.error(e);
}
}
}
delete pv.$;
});
The technique I've used to use "text/javascript" and avoid using "text/javascript+protovis" both solves your problem AND makes it easier to debug code using protovis in Firefox.
Great job James - only one thing to watch out for: If you keep the createLayout(); call within the jQuery $(document).ready() function you might find your panel appearing in the wrong place... if you want the panel to appear within the div your script is in, remove the jQuery refs and all should be fine.
Edit:
I wasn't aware of the canvas parameter in Protovis at the time I wrote this - simply adding canvas divid to the panel, plus a div with that id, takes care of positioning issues completely.
加载中,请稍侯......
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