Develop Reference

Appended bars wont draw on svg element

I am trying to write a transitioning bar graph that uses two CVS files. I know that both of the files are loading properly because it shows in the console that the first one loads with the page and the second one loads when you click the update button.
The only thing that I have really thought of trying was changing the svg select to group instead of selecting all rectangles incase there was something screwed up there.
This block is creating the svg element, bringing in the first CSV file, and appending the rectangles onto the chart. My only thought for what the problem could be is that it is inside a function, but if I take it out of the function how do I bind the data to them?
//Creating SVG Element
var chart_w = 1000,
chart_h = 500,
chart_pad_x = 40,
chart_pad_y = 20;
var svg = d3.select('#chart')
.append('svg')
.attr('width', chart_w)
.attr('height', chart_h);
//Defining Scales
var x_scale = d3.scaleBand().range([chart_pad_x, chart_w -
chart_pad_x]).padding(0.2);
var y_scale = d3.scaleLinear().range([chart_pad_y, chart_h -
chart_pad_y]);
//Data-------------------------------------------------------------------
d3.csv('data.csv').then(function(data){
console.log(data);
generate(data); });
function generate(data){
//Scale domains
x_scale.domain(d3.extent(data, function(d){ return d }));
y_scale.domain([0, d3.max(data, function(d){ return d })]);
//Create Bars
svg.select('rect')
.data(data)
.enter()
.append('rect')
.attr('x', function(d, i){
return x_scale(i);
})
.attr('y', function(d){
return y_scale(d);
})
.attr('width', x_scale.bandwidth())
.attr('height', function(d){
return y_scale(d);
})
.attr('transform',
"translate(0,0)")
.attr('fill', '#03658C')
'''
The results I have experienced is a blank window with just the update button. As previously stated I know that the data is being generated because I can see it in the console.

Try using the following:
svg.selectAll('rect')
.data(data)
If you use svg.select this will only make the data binding with the first element found.
d3.select(selector): Selects the first element that matches the specified selector string. If no elements match the selector, returns an empty selection. If multiple elements match the selector, only the first matching element (in document order) will be selected. For example, to select the first anchor element:
This should be clear if you inspect the DOM nodes.
To fix the issue lets change some things in your code:
Lets create a dummy fetch function:
(function simulateCSVFetch() {
const data = [1,2,3,4,5];
generate(data);
})();
You are also using a scaleBand with an incomplete domain by using the extent function:
d3.extent(): Returns the minimum and maximum value in the given iterable using natural order. If the iterable contains no comparable values, returns [undefined, undefined]. An optional accessor function may be specified, which is equivalent to calling Array.from before computing the extent.
x_scale.domain(d3.extent(data, function(d) { // cant use extent since we are using a scaleBand, we need to pass the whole domain
return d;
}));
console.log(x_scale.domain()) // [min, max]
The scaleBand needs the whole domain to be mapped
Band scales are typically used for bar charts with an ordinal or categorical dimension. The unknown value of a band scale is effectively undefined: they do not allow implicit domain construction.
If we continue using that scale we will be only to get two values for our x scale. Lets fix that with the correct domain:
x_scale.domain(data);
Lastly use the selectAll to create the data bind:
svg.selectAll('rect')
.data(data)
.enter()
.append('rect')
.attr('x', function(d, i) {
return x_scale(d);
})
.attr('y', function(d) {
return chart_h - y_scale(d); // fix y positioning
})
.attr('width', x_scale.bandwidth())
.attr('height', function(d) {
return y_scale(d);
})
.attr('fill', '#03658C');
This should do the trick.
Complete code:
var chart_w = 1000,
chart_h = 500,
chart_pad_x = 40,
chart_pad_y = 20;
var svg = d3
.select('#chart')
.append('svg')
.style('background', '#f9f9f9')
.style('border', '1px solid #cacaca')
.attr('width', chart_w)
.attr('height', chart_h);
//Defining Scales
var x_scale = d3.scaleBand()
.range([chart_pad_x, chart_w - chart_pad_x])
.padding(0.2);
var y_scale = d3.scaleLinear()
.range([chart_pad_y, chart_h - chart_pad_y]);
//Data-------------------------------------------------------------------
(function simulateCSVFetch() {
const data = [1,2,3,4,5];
generate(data);
})();
function generate(data) {
console.log(d3.extent(data, function(d) { return d }));
//Scale domains
x_scale.domain(d3.extent(data, function(d) { // cant use extent since we are using a scaleBand, we need to pass the whole domain
return d;
}));
// Band scales are typically used for bar charts with an ordinal or categorical dimension. The unknown value of a band scale is effectively undefined: they do not allow implicit domain construction.
x_scale.domain(data);
y_scale.domain([0, d3.max(data, function(d) {
return d
})]);
//Create Bars
svg.selectAll('rect')
.data(data)
.enter()
.append('rect')
.attr('x', function(d, i) {
return x_scale(d);
})
.attr('y', function(d) {
return chart_h - y_scale(d); // fix y positioning
})
.attr('width', x_scale.bandwidth())
.attr('height', function(d) {
return y_scale(d);
})
.attr('fill', '#03658C');
}
Working jsfiddle here

apply a transition on each object in a D3 selection

I'm having troubles in understanding how to get each D3 object in a selection to apply a transition.
Consider the follwoing code (here on jsfiddle):
var svg = d3.select('svg');
var dataSet = [10, 20, 30, 40];
var circle = svg.selectAll('circle')
.data(dataSet)
.enter()
.append('circle')
.attr("r",function(d){ return d })
.attr("cx", function(d, i){ return i * 100 + Math.random()*50 })
.attr("cy",50)
.attr("fill",'red')
;
circle.each(function(d,i) {
this
.transition()
.duration(1000)
.attr("cx",this.cx+100);
})
My use of this is wrong. I've also tried with d3.select(this) but I get the dom object corresponding to D3 object.
I'm unable to get the D3 object to apply transition.

The missing part is that you can supply a function to .attr('cx', function (d,i) { ... }) when using a transition, and inside that function you can access the cx attribute using this.getAttribute('cx').
Of course, you also want to make sure to turn it into a number using parseInt(), otherwise it will do string concatenation (because JS, sigh).
So change your final line to:
circle.transition().duration(1000).attr('cx', function(d, i) {
return parseInt(this.getAttribute('cx')) + 100;
});

D3 not updating label

I have a map and a matching legend on my website. As the user selects different values from a select list, the map is updated and in the same function, the legend should be updated with new values. As the map actualization works properly, the values of the legend stay the same even in the console are logged the right values if I log the variables.
This is the function that draws the legend:
color_domain = [wert1, wert2, wert3, wert4, wert5];
ext_color_domain = [0, wert1, wert2, wert3, wert4, wert5];
console.log(ext_color_domain);
legend_labels = ["< "+wert1, ""+wert1, ""+wert2, ""+wert3, ""+wert4, "> "+wert5];
color = d3.scale.threshold()
.domain(color_domain)
.range(["#85db46", "#ffe800", "#ffba00", "#ff7d73", "#ff4e40", "#ff1300"]);
var legend = svg.selectAll("g.legend")
.data(ext_color_domain)
.enter().append("g")
.attr("class", "legend");
var ls_w = 20, ls_h = 20;
legend.append("rect")
.attr("x", 20)
.attr("y", function(d, i){ return height - (i*ls_h) - 2*ls_h;})
.attr("width", ls_w)
.attr("height", ls_h)
.style("fill", function(d, i) { return color(d); })
.style("opacity", 0.7);
legend.append("text")
.attr("x", 50)
.attr("y", function(d, i){ return height - (i*ls_h) - ls_h - 4;})
.text(function(d, i){ return legend_labels[i]; });
console.log(legend_labels); //gives the right legend_labels but doesn't display them correctly
};
Sadly even the map is updated with new colors they're colored with the old thresholds. This is the way the map is colored:
svg.append("g")
.attr("class", "id")
.selectAll("path")
.data(topojson.feature(map, map.objects.immoscout).features)
.enter().append("path")
.attr("d", path)
.style("fill", function(d) {
return color(rateById[d.id]);
})

This is tough to answer without a complete, working code sample but...
You are not handling the enter, update, exit pattern correctly. You never really update existing elements, you are only re-binding data and entering new ones.
Say you've called your legend function once already, now you have new data and you do:
var legend = svg.selectAll("g.legend")
.data(ext_color_domain)
.enter().append("g")
.attr("class", "legend");
This re-binds the data and computes an enter selection. It says, hey d3, what data elements are new? For those new ones, you then append a g. Further:
legend.append("rect")
.attr("x", 20)
.attr("y", function(d, i){ return height - (i*ls_h) - 2*ls_h;})
.attr("width", ls_w)
.attr("height", ls_h)
.style("fill", function(d, i) { return color(d); })
.style("opacity", 0.7);
Again, this is operating on those newly entered elements only. The ones that already existed on the page aren't touched at all.
Untested code, but hopefully it points you in the right direction:
// selection of all enter, update, exit
var legend = svg.selectAll("g.legend")
.data(ext_color_domain); //<-- a key function would be awesome here
legend.exit().remove(); //<-- did the data go away? remove the g bound to it
// ok, what data is coming in? create new elements;
var legendEnter = legend.enter().append("g")
.attr("class", "legend");
legendEnter.append("rect");
legendEnter.append("text");
// ok, now handle our updates...
legend.selectAll("rect")
.attr("x", 20)
.attr("y", function(d, i){ return height - (i*ls_h) - 2*ls_h;})
.attr("width", ls_w)
.attr("height", ls_h)
.style("fill", function(d, i) { return color(d); })
.style("opacity", 0.7);
legend.selectall("text")
...
There's some really great tutorials on this; and it's confusing as hell, but it's the foundation of d3.

An example that helps you get started with updating d3 (d3, v4):
const line = svg.selectAll('line').data(d3Data); // binds things
line.exit().remove(); // removes old data
line.enter()
.append('line') // add new lines for new items on enter
.merge(line) // <--- this will make the updates to the lines
.attr('fill', 'none')
.attr('stroke', 'red');

how to pass returned data stored as a variable from a d3.json call as an argument to circle radius

This is bugging me little bit. I am making a d3.get.json with a callback to retrieve some data from an api. Works great. Then I am storing the key value in a variable which I am trying to pass as an argument to a circle. And that wont work. The circle wont get drawn. Cant seem to figure out what I am doing wrong
This is what I have
d3.json("http://data.cityofnewyork.us/resource/xm9j-adfx.json", function(data) {
var energy = JSON.parse(data[0].consumption_gj_)/1000; // I probably will figure out a better math function for this
//alert(energy)
var x_axis = 10;
var y_axis = 10;
var svgContainer = d3.select("#chart").append("svg")
.attr("width", 300)
.attr("height", 300)
.style("background", "black");
var circles = svgContainer.selectAll("circle")
.data(json)
.enter()
.append("circle");
var circleAttributes = circles
.attr("cx", function(d){return d.x_axis;} )
.attr("cx", function(d){return d.y_axis;} )
.attr("r", function(d){return d.energy;} )
.style("fill", "red");
});
Basically the idea is to draw the circle with a radius as a function to the energy variable
Here is my fiddle
http://jsfiddle.net/sghoush1/KcWCr/5/

You need to call .data(data) and not .data(json) and you'll get the circles drawn.
You still need to to assign the circle attributes this way:
.attr("cx", function(d){return d.x_axis;} )

ok for anyone who might be wondering how to resolve this....I just figured it myself...
here is the fiddle..(pat on my back)
http://jsfiddle.net/sghoush1/KcWCr/6/
The idea is once i store data in a variable using the callback fro the d3.json, I can easily use it as an argument to any attribute or style for generating shapes. Here is how I did it
d3.json("the external .json ", function(data) {
var blablbla = JSON.parse(whatever key value I want to parse);
//alert(energy)
var x_axis = 10;
var y_axis = 10;
var svgContainer = d3.select("#chart").append("svg")
.attr("width", 300)
.attr("height", 300)
.style("background", "black");
var circles = svgContainer.selectAll("circle")
.data(data)
.enter()
.append("circle");
var circleAttributes = circles
.attr("cx", "50" )
.attr("cy", "50" )
.attr("r", function(d){return blablbla;} )
.style("fill", "red");
});
and bingo!!

D3 - how to deal with JSON data structures?

I'm new to D3, and spent already a few hours to find out anything about dealing with structured data, but without positive result.
I want to create a bar chart using data structure below.
Bars are drawn (horizontally), but only for user "jim".
var data = [{"user":"jim","scores":[40,20,30,24,18,40]},
{"user":"ray","scores":[24,20,30,41,12,34]}];
var chart = d3.select("div#charts").append("svg")
.data(data)
.attr("class","chart")
.attr("width",800)
.attr("height",350);
chart.selectAll("rect")
.data(function(d){return d3.values(d.scores);})
.enter().append("rect")
.attr("y", function(d,i){return i * 20;})
.attr("width",function(d){return d;})
.attr("height", 20);
Could anyone point what I did wrong?

When you join data to a selection via selection.data, the number of elements in your data array should match the number of elements in the selection. Your data array has two elements (for Jim and Ray), but the selection you are binding it to only has one SVG element. Are you trying to create multiple SVG elements, or put the score rects for both Jim and Ray in the same SVG element?
If you want to bind both data elements to the singular SVG element, you can wrap the data in another array:
var chart = d3.select("#charts").append("svg")
.data([data])
.attr("class", "chart")
…
Alternatively, use selection.datum, which binds data directly without computing a join:
var chart = d3.select("#charts").append("svg")
.datum(data)
.attr("class", "chart")
…
If you want to create multiple SVG elements for each person, then you'll need a data-join:
var chart = d3.select("#charts").selectAll("svg")
.data(data)
.enter().append("svg")
.attr("class", "chart")
…
A second problem is that you shouldn't use d3.values with an array; that function is for extracting the values of an object. Assuming you wanted one SVG element per person (so, two in this example), then the data for the rect is simply that person's associated scores:
var rect = chart.selectAll("rect")
.data(function(d) { return d.scores; })
.enter().append("rect")
…
If you haven't already, I recommend reading these tutorials:
Thinking with Joins
Nested Selections

This may clarify the nested aspect, in addition to mbostock's fine answer.
Your data has 2 degrees of nesting. You have an array of 2 objects, each has an array of ints. If you want your final image to reflect these differences, you need to do a join for each.
Here's one solution: Each user is represented by a group g element, with each score represented by a rect. You can do this a couple of ways: Either use datum on the svg, then an identity function on each g, or you can directly join the data on the g. Using data on the g is more typical, but here are both ways:
Using datum on the svg:
var chart = d3.select('body').append('svg')
.datum(data) // <---- datum
.attr('width',800)
.attr('height',350)
.selectAll('g')
.data(function(d){ return d; }) // <----- identity function
.enter().append('g')
.attr('class', function(d) { return d.user; })
.attr('transform', function(d, i) { return 'translate(0, ' + i * 140 + ')'; })
.selectAll('rect')
.data(function(d) { return d.scores; })
.enter().append('rect')
.attr('y', function(d, i) { return i * 20; })
.attr('width', function(d) { return d; })
.attr('height', 20);
Using data on the group (g) element:
var chart = d3.select('body').append('svg')
.attr('width',800)
.attr('height',350)
.selectAll('g')
.data(data) // <--- attach directly to the g
.enter().append('g')
.attr('class', function(d) { return d.user; })
.attr('transform', function(d, i) { return 'translate(0, ' + i * 140 + ')'; })
.selectAll('rect')
.data(function(d) { return d.scores; })
.enter().append('rect')
.attr('y', function(d, i) { return i * 20; })
.attr('width', function(d) { return d; })
.attr('height', 20);
Again, you don't have to create these g elements, but by doing so I can now represent the user scores differently (they have different y from the transform) and I can also give them different styles, like this:
.jim {
fill: red;
}
.ray {
fill: blue;
}