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(function() {
d3.horizon = function() {
var bands = 1, // between 1 and 5, typically
mode = "offset", // or mirror
interpolate = "linear", // or basis, monotone, step-before, etc.
x = d3_horizonX,
y = d3_horizonY,
w = 960,
h = 40,
duration = 0;
var color = d3.scale.linear()
.domain([-1, 0, 1])
.range(["#d62728", "#fff", "#1f77b4"]);
// For each small multiple…
function horizon(g) {
g.each(function(d, i) {
var g = d3.select(this),
n = 2 * bands + 1,
xMin = Infinity,
xMax = -Infinity,
yMax = -Infinity,
x0, // old x-scale
y0, // old y-scale
id; // unique id for paths
// Compute x- and y-values along with extents.
var data = d.map(function(d, i) {
var xv = x.call(this, d, i),
yv = y.call(this, d, i);
if (xv < xMin) xMin = xv;
if (xv > xMax) xMax = xv;
if (-yv > yMax) yMax = -yv;
if (yv > yMax) yMax = yv;
return [xv, yv];
});
// Compute the new x- and y-scales, and transform.
var x1 = d3.scale.linear().domain([xMin, xMax]).range([0, w]),
y1 = d3.scale.linear().domain([0, yMax]).range([0, h * bands]),
t1 = d3_horizonTransform(bands, h, mode);
// Retrieve the old scales, if this is an update.
if (this.__chart__) {
x0 = this.__chart__.x;
y0 = this.__chart__.y;
t0 = this.__chart__.t;
id = this.__chart__.id;
} else {
x0 = x1.copy();
y0 = y1.copy();
t0 = t1;
id = ++d3_horizonId;
}
// We'll use a defs to store the area path and the clip path.
var defs = g.selectAll("defs")
.data([null]);
// The clip path is a simple rect.
defs.enter().append("defs").append("clipPath")
.attr("id", "d3_horizon_clip" + id)
.append("rect")
.attr("width", w)
.attr("height", h);
defs.select("rect").transition()
.duration(duration)
.attr("width", w)
.attr("height", h);
// We'll use a container to clip all horizon layers at once.
g.selectAll("g")
.data([null])
.enter().append("g")
.attr("clip-path", "url(#d3_horizon_clip" + id + ")");
// Instantiate each copy of the path with different transforms.
var path = g.select("g").selectAll("path")
.data(d3.range(-1, -bands - 1, -1).concat(d3.range(1, bands + 1)), Number);
var d0 = d3_horizonArea
.interpolate(interpolate)
.x(function(d) { return x0(d[0]); })
.y0(h * bands)
.y1(function(d) { return h * bands - y0(d[1]); })
(data);
var d1 = d3_horizonArea
.x(function(d) { return x1(d[0]); })
.y1(function(d) { return h * bands - y1(d[1]); })
(data);
path.enter().append("path")
.style("fill", color)
.attr("transform", t0)
.attr("d", d0);
path.transition()
.duration(duration)
.style("fill", color)
.attr("transform", t1)
.attr("d", d1);
path.exit().transition()
.duration(duration)
.attr("transform", t1)
.attr("d", d1)
.remove();
// Stash the new scales.
this.__chart__ = {x: x1, y: y1, t: t1, id: id};
});
d3.timer.flush();
}
horizon.duration = function(x) {
if (!arguments.length) return duration;
duration = +x;
return horizon;
};
horizon.bands = function(x) {
if (!arguments.length) return bands;
bands = +x;
color.domain([-bands, 0, bands]);
return horizon;
};
horizon.mode = function(x) {
if (!arguments.length) return mode;
mode = x + "";
return horizon;
};
horizon.colors = function(x) {
if (!arguments.length) return color.range();
color.range(x);
return horizon;
};
horizon.interpolate = function(x) {
if (!arguments.length) return interpolate;
interpolate = x + "";
return horizon;
};
horizon.x = function(z) {
if (!arguments.length) return x;
x = z;
return horizon;
};
horizon.y = function(z) {
if (!arguments.length) return y;
y = z;
return horizon;
};
horizon.width = function(x) {
if (!arguments.length) return w;
w = +x;
return horizon;
};
horizon.height = function(x) {
if (!arguments.length) return h;
h = +x;
return horizon;
};
return horizon;
};
var d3_horizonArea = d3.svg.area(),
d3_horizonId = 0;
function d3_horizonX(d) {
return d[0];
}
function d3_horizonY(d) {
return d[1];
}
function d3_horizonTransform(bands, h, mode) {
return mode == "offset"
? function(d) { return "translate(0," + (d + (d < 0) - bands) * h + ")"; }
: function(d) { return (d < 0 ? "scale(1,-1)" : "") + "translate(0," + (d - bands) * h + ")"; };
}
})();
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