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How can I dynamically update text labels in d3?

I want to add labels to my vertical bar chart that display the current percentage value that corresponds to the current hight of the bar.
So I need to continuously update the percentage value and I also need a transition to make the text element move insync with the bar chart.
I tried this:
var percentageLabels = svg.selectAll(".percentage-label")
.data(dataset);
percentageLabels.remove();
percentageLabels
.enter()
.append("text")
.attr("class", "percentage-label")
.style("fill", "white")
.text(function(d) {
return d;
})
.attr("y", function(d) {
return y(d);
})
.attr("x", function(d, i) {
return i * (w / dataset.length) + 2.5 / 100 * w + w * 10/100;
})
.transition().duration(1750).ease("linear")
.attr("y", function(d) {
return y(d);
});
Check out the fiddle

I'd make a couple changes here. First, wrap the rect and the text in a g, so you only need to data-bind once. Then you are free to transition them together:
var uSel = svg.selectAll(".input")
.data(dataset); //<-- selection of gs
uSel.exit().remove(); //<-- anybody leaving? remove g (both rect and text)
var gs = uSel
.enter()
.append("g")
.attr("class", "input"); //<-- enter selection, append g
gs.append("rect")
.attr("fill", "rgb(250, 128, 114)"); //<-- enter selection, rect to g
gs.append("text")
.attr("class", "percentage-label")
.style("fill", "white")
.attr("x", function(d, i) {
return i * (w / dataset.length) + 2.5 / 100 * w + w * 10/100;
}); //<-- enter selection, text to g
uSel.select("rect")
.attr("x", function(d, i) {
return i * (w / dataset.length) + 2.5 / 100 * w;
})
.attr("width", w / dataset.length - barPadding)
.attr("height", y(0))
.transition().duration(1750).ease("linear")
.attr("y", function(d) {
return y(d);
})
.attr("height", function(d) {
return h - y(d);
}); //<-- update rects with transition
uSel.select("text")
.transition().duration(1750).ease("linear")
.attr("y", function(d) {
return y(d);
})
.text(function(d) {
return d + "%";
}); //<-- update text with transition
Updated fiddle.
EDITS
To transition the text, you are probably going to have to use a custom tween function:
uSel.select("text")
.transition().duration(1750).ease("linear")
.attr("y", function(d) {
return y(d); //<-- move the text
})
.tween("", function(d) {
var self = d3.select(this),
oldValue = y.invert(self.attr("y")), //<-- get the current value
i = d3.interpolateRound(oldValue, d); //<-- interpolate to new value
return function(t) {
self.text(i(t) + '%') <-- update the text on each iteration
};
});
Updated, updated fiddle.

From the docs:
The transition.each method can be used to chain transitions and apply shared timing across a set of transitions. For example:
d3.transition()
.duration(750)
.ease("linear")
.each(function() {
d3.selectAll(".foo").transition()
.style("opacity", 0)
.remove();
})
.transition()
.each(function() {
d3.selectAll(".bar").transition()
.style("opacity", 0)
.remove();
});

You might want to check out this: https://github.com/mbostock/d3/wiki/Transitions#tween

D3: Attach text to circle such that it has same priority as circle object

I am able to add text to my sketch, but I would like it if I could make my text attached directly to the circle. This means that if a circle gets over-written by another circle, the text will as well. On a higher level not, I am finding the d3 model hard for constructing objects in a way that makes them composable with different shapes, etc. The code seems very procedural to mean so any tips would be greatly appeciated :)
JSFiddle link
var link = "https://api.github.com/orgs/csci-4830-002-2014/repos"
d3.json(link, function(error, data) {
var w = 10000;
var h = 1000;
var svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
svg.selectAll("line")
.data(data)
.enter()
.append("line")
.attr("x1", 5)
.attr("y1", 5)
.attr("x2", function (d,i){
return 30*d.forks_count;
})
.attr("y2", function (d,i){
return 30*d.open_issues_count;
})
.attr("stroke-width", 2)
.attr("stroke", "black");
svg.selectAll("circle")
.data(data)
.enter()
.append("circle")
.attr("r", 40)
.attr("cx", function(d){ return 30*d.forks_count; })
.attr("cy", function(d){ return 30*d.open_issues_count; })
.attr("stroke", "black")
.attr("stroke-width", 2)
.attr("fill", "white")
svg.selectAll("text")
.data(data)
.enter()
.append("text")
.attr("dx", function(d,i){ return 30*d.forks_count; })
.attr("dy", function(d,i){ return 30*d.open_issues_count; })
.text(function(d){
if (d.name.indexOf("challenge") != -1)
return "C";
else
return "H";
});
});

With the way your code written right now, all the lines will be added first, then all the circles, and finally the texts. SVG will always put elements added later on top. So to achieve what you want, you will need to group them up. To do this, you will need to add a g element for each element of your data
var element = svg.selectAll(".element")
.data(data)
.enter()
.append("g")
.attr("class","element");
Now you can add the line, circle, and text to it
element.append("line")
.attr("x1", 5)
.attr("y1", 5)
.attr("x2", function (d, i) {
return 30 * d.forks_count;
})
.attr("y2", function (d, i) {
return 30 * d.open_issues_count;
})
.attr("stroke-width", 2)
.attr("stroke", "black");
element.append("circle")
.attr("r", 30)
.attr("cx", function (d) {
return 30 * d.forks_count;
})
.attr("cy", function (d) {
return 30 * d.open_issues_count;
})
.attr("stroke", "black")
.attr("stroke-width", 2)
.attr("fill", "white")
element
.append("text")
.attr("dx", function (d, i) {
return 30 * d.forks_count;
})
.attr("dy", function (d, i) {
return 30 * d.open_issues_count+6;
})
.style("text-anchor", "middle")
.text(function (d) {
if (d.name.indexOf("challenge") != -1) return "C";
else return "H";
});
You can check the updated JSFiddle at http://jsfiddle.net/9tp1yun7/2/

Chart not updating properly

I am trying to follow Mike Bostock's tutorial on d3js (http://mbostock.github.io/d3/tutorial/bar-2.html) to understand how to update charts dynamically but I am facing some hurdles.
In my chart, my bars on the left, rather than being simply removed, are sent behind my chart and I can't figure out why:
JS:
var t = 1297110663, // start time (seconds since epoch)
v = 70, // start value (subscribers)
data = d3.range(33).map(next); // starting dataset
function next() {
return {
time: ++t,
value: v = ~~Math.max(10, Math.min(90, v + 10 * (Math.random() - .5)))
};
}
setInterval(function(){
data.shift();
data.push(next());
console.log(data);
redraw();
}, 1000);
var w = 20,
h =80;
var x = d3.scale.linear()
.domain([0, 1])
.range([0, w]);
var y = d3.scale.linear()
.domain([0, 100])
.rangeRound([0, h]);
var chart = d3.select(".container").append("svg")
.attr("class", "chart")
.attr("width", w * data.length - 1)
.attr("height", h);
chart.selectAll("rect")
.data(data)
.enter().append("rect")
.attr("x", function(d, i){ return x(i) - 0.5; })
.attr("y", function(d) { return h - y(d.value) - .5; })
.attr("width", w)
.attr("height", function(d) { return y(d.value); });
function redraw(){
console.log(data);
var rect = chart.selectAll('rect')
.data(data, function(d){ return d.time; });
rect.enter().insert("rect")
.attr("x", function(d, i) { return x(i + 1) - .5; })
.attr("y", function(d) { return h - y(d.value) - .5; })
.attr("width", w)
.attr("height", function(d) { return y(d.value); })
rect.transition() // Shouldn't I use .update() here?
.duration(1000)
.attr("x", function(d, i) { return x(i) - .5; });
rect.exit().transition()
.duration(1000)
.attr('x', function(d, i) { return x(i - 1) - .5})
.remove();
}
Here is the jsfiddle: http://jsfiddle.net/kkMR4/
Another thing I don't understand is why we dont use .update()? If I understand correctly .enter() is used to create the DOM element where data didnt find any match in the DOM and .exit() is used to find the DOM elements which are not in data, so shouldn't I use update() to move all the other column to the left?
Many thanks
Best

The problem is in this block:
rect.exit().transition()
.duration(1000)
.attr('x', function(d, i) { return x(i - 1) - .5})
.remove();
The third line (.attr), reassigns the coordinates. If you want them to truly exit, you can remove this line.
rect.exit().transition()
.duration(1000)
.remove();

How to access attributes of an element inside a group?

I'm not sure if I've grouped my elements properly, but my layout in d3 is like so:
var circleGroup = svg.selectAll("g")
.data(nodeList)
.enter()
.append("g")
This creates a bunch a groups, I need a circle in each group:
circleGroup.append("circle")
.attr("cx", function(d,i){
return coordinates[i][0];
})
.attr("cy", function(d,i){
return coordinates[i][1];
})
.attr("r", function(d){
return 10;
})
.attr("fill", "white");
The data itself doesn't actually have any coordinate data so I dynamically arrange them in a circle and just position them based on index. I also add some labels. I repeat coordinates[i][0] here but is there a way to access the "cx" and "cy" attributes of the circles? I tried a few forms of d3.select(this) but I'm getting nothing.
circleGroup.append("text")
.attr("x", function(d,i){
return coordinates[i][0];
})
.attr("y", function(d,i){
return coordinates[i][1];
})
.style("text-anchor","middle")
.text(function(d,i){
return d;
});

Don't mess with indices, this is hard to maintain and error prone. Instead of that, given your specific tree structure, use node.previousSibling:
circleGroup.append("text")
.attr("x", function() {
return d3.select(this.previousSibling).attr("cx");
})
.attr("y", function() {
return d3.select(this.previousSibling).attr("cy");
})
Here is a demo using (most of) your code:
var svg = d3.select("svg")
var circleGroup = svg.selectAll("g")
.data(d3.range(5))
.enter()
.append("g");
circleGroup.append("circle")
.attr("cx", function(d, i) {
return 20 + Math.random() * 280;
})
.attr("cy", function(d, i) {
return 20 + Math.random() * 130;
})
.attr("r", function(d) {
return 10;
})
.style("opacity", 0.2);
circleGroup.append("text")
.attr("x", function() {
return d3.select(this.previousSibling).attr("cx");
})
.attr("y", function() {
return d3.select(this.previousSibling).attr("cy");
})
.style("text-anchor", "middle")
.text("Foo");
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
<svg></svg>

d3.js adding legend to multiline series chart

How would one add a legend to the multiline series chart? I tried but am not getting any legend to display.
The block here:
http://bl.ocks.org/3884955
has a flaw when the various series converge to the same point, like zero. All the labels will be overlayed on each other. Instead of going for these labels, a traditional legend would be useful.
I tried adding this
var legend = svg.append("g")
.attr("class", "legend")
.attr("height", 100)
.attr("width", 100)
.attr('transform', 'translate(-20,50)');
legend.selectAll('rect')
.datum(function(d) { return {name: d.name, value: d.values[d.values.length - 1]}; })
.append("rect")
.attr("x", width)
.attr("y", function(d, i){ return i * 20;})
.attr("width", 10)
.attr("height", 10)
.style("fill", function(d) {
return color.domain(d3.keys(d[0]).filter(function(key) { return key !== "day"; }));
});
legend.selectAll('text')
.datum(function(d) { return {name: d.name, value: d.values[d.values.length - 1]}; })
.append("text")
.attr("x", width)
.attr("y", function(d, i){ return i * 20 + 9;})
.text(function(d) {
return d.name;
});
to the end of the code, the key names (d.name) match how my data is formatted, but it does not display. At one point it showed all black boxes to the right of the graph so that means I am close but I am missing something important
any insight appreciated

Here is a fixed & refactored version of your code.
var legend = svg.selectAll('g')
.data(cities)
.enter()
.append('g')
.attr('class', 'legend');
legend.append('rect')
.attr('x', width - 20)
.attr('y', function(d, i){ return i * 20;})
.attr('width', 10)
.attr('height', 10)
.style('fill', function(d) {
return color(d.name);
});
legend.append('text')
.attr('x', width - 8)
.attr('y', function(d, i){ return (i * 20) + 9;})
.text(function(d){ return d.name; });
You need to use enter(), but enter() and exit() methods cannot be used with datum(). Quoting from the d3 wiki
selection.datum([value])
Gets or sets the bound data for each selected element. Unlike the selection.data method, this method does not compute a join (and thus does not compute enter and exit selections).

You seem to be missing the .enter() after .datum() function call.
legend.selectAll('rect')
.datum(function(d) { return {name: d.name, value: d.values[d.values.length - 1]}; })
.enter() // <======
.append("rect")
.attr("x", width)
.attr("y", function(d, i){ return i * 20;})
.attr("width", 10)
.attr("height", 10)
.style("fill", function(d) {
return color.domain(d3.keys(d[0]).filter(function(key) { return key !== "day"; }));
Before appending the "rect" you must use the enter() function see link for exact explanation Click Here