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@mbostock
Last active Jan 10, 2023
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Margin Convention
license: gpl-3.0
redirect: https://observablehq.com/@d3/margin-convention

First define the margin object with properties for the four sides (clockwise from the top, as in CSS).

var margin = {top: 20, right: 10, bottom: 20, left: 10};

Then define width and height as the inner dimensions of the chart area.

var width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

Lastly, define svg as a G element that translates the origin to the top-left corner of the chart area.

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

With this convention, all subsequent code can ignore margins. For example, to create x and y scales, simply say:

var x = d3.scale.linear()
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

If you want to add axes to the chart, they will be positioned correctly by default in the "left" and "top" orientations. For "right" or "bottom" orientation, translate the axis G element by the width or height, respectively.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font: 10px sans-serif;
}
.axis line,
.axis path {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.arrow {
stroke: #000;
stroke-width: 1.5px;
}
.outer,
.inner {
shape-rendering: crispEdges;
}
.outer {
fill: none;
stroke: #000;
}
.inner {
fill: #ccc;
stroke: #000;
stroke-dasharray: 3, 4;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 20, right: 20, bottom: 20, left: 20},
padding = {top: 60, right: 60, bottom: 60, left: 60},
outerWidth = 960,
outerHeight = 500,
innerWidth = outerWidth - margin.left - margin.right,
innerHeight = outerHeight - margin.top - margin.bottom,
width = innerWidth - padding.left - padding.right,
height = innerHeight - padding.top - padding.bottom;
var x = d3.scale.identity()
.domain([0, width]);
var y = d3.scale.identity()
.domain([0, height]);
var xAxis = d3.svg.axis()
.scale(x)
.orient("bottom");
var yAxis = d3.svg.axis()
.scale(y)
.orient("right");
var svg = d3.select("body").append("svg")
.attr("width", outerWidth)
.attr("height", outerHeight)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
var defs = svg.append("defs");
defs.append("marker")
.attr("id", "triangle-start")
.attr("viewBox", "0 0 10 10")
.attr("refX", 10)
.attr("refY", 5)
.attr("markerWidth", -6)
.attr("markerHeight", 6)
.attr("orient", "auto")
.append("path")
.attr("d", "M 0 0 L 10 5 L 0 10 z");
defs.append("marker")
.attr("id", "triangle-end")
.attr("viewBox", "0 0 10 10")
.attr("refX", 10)
.attr("refY", 5)
.attr("markerWidth", 6)
.attr("markerHeight", 6)
.attr("orient", "auto")
.append("path")
.attr("d", "M 0 0 L 10 5 L 0 10 z");
svg.append("rect")
.attr("class", "outer")
.attr("width", innerWidth)
.attr("height", innerHeight);
var g = svg.append("g")
.attr("transform", "translate(" + padding.left + "," + padding.top + ")");
g.append("rect")
.attr("class", "inner")
.attr("width", width)
.attr("height", height);
g.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis);
g.append("g")
.attr("class", "y axis")
.attr("transform", "translate(" + width + ",0)")
.call(yAxis);
svg.append("line")
.attr("class", "arrow")
.attr("x2", padding.left)
.attr("y2", padding.top)
.attr("marker-end", "url(#triangle-end)");
svg.append("line")
.attr("class", "arrow")
.attr("x1", innerWidth / 2)
.attr("x2", innerWidth / 2)
.attr("y2", padding.top)
.attr("marker-end", "url(#triangle-end)");
svg.append("line")
.attr("class", "arrow")
.attr("x1", innerWidth / 2)
.attr("x2", innerWidth / 2)
.attr("y1", innerHeight - padding.bottom)
.attr("y2", innerHeight)
.attr("marker-start", "url(#triangle-start)");
svg.append("line")
.attr("class", "arrow")
.attr("x2", padding.left)
.attr("y1", innerHeight / 2)
.attr("y2", innerHeight / 2)
.attr("marker-end", "url(#triangle-end)");
svg.append("line")
.attr("class", "arrow")
.attr("x1", innerWidth)
.attr("x2", innerWidth - padding.right)
.attr("y1", innerHeight / 2)
.attr("y2", innerHeight / 2)
.attr("marker-end", "url(#triangle-end)");
svg.append("text")
.text("origin")
.attr("y", -8);
svg.append("circle")
.attr("class", "origin")
.attr("r", 4.5);
g.append("text")
.text("translate(margin.left, margin.top)")
.attr("y", -8);
</script>
@walterdavis
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This is really cool. How would you get it to flex with the page, though? If you wanted to change the dimensions to respond to a screen orientation change, for example?

@riccardoscalco
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For who is interested in your question: http://codepen.io/riccardoscalco/pen/pJPYmE

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