Limiting domain when zooming or panning in D3.js

Question

I have implemented a simple D3.js line chart that can be zoomed and panned. It is based on Stephen Bannasch\'s excellent example here.

The domain of my data is [0, n

Answer 1

Sadly, the solution posted by Bill did only half the trick: While it does indeed inhibit the panning, it causes the graph to distort if zoom is applied. It is then usually impossible to return to a properly proportioned and positioned graph.

In the following version the proportions of the axes are maintained, even if scrolling to the borders.

As soon as the scaling hits 100%, the scales' domains are reset to their original position. This guarantees a correct positioning, even if the intermediate steps return illegal parameters for the axes.

While not perfect, I hope this script can help somebody until d3 (re)implements this feature.

# x and y are the scales
# xAxis and yAxis are the axes
# graph is the graph you want attach the zoom to

x0 = x.copy()
y0 = y.copy()

successfulTranslate = [0, 0]

zoomer = d3.behavior.zoom()
  .scaleExtent([1,2])

onZoom = ->
  ev = d3.event # contains: .translate[x,y], .scale
  if ev.scale == 1.0
    x.domain x0.domain()
    y.domain y0.domain()
    successfulTranslate = [0, 0]
  else
    xTrans = x0.range().map( (xVal) -> (xVal-ev.translate[0]) / ev.scale ).map(x0.invert)
    yTrans = y0.range().map( (yVal) -> (yVal-ev.translate[1]) / ev.scale ).map(y0.invert)
    xTransOk = xTrans[0] >= x0.domain()[0] and xTrans[1] <= x0.domain()[1]
    yTransOk = yTrans[0] >= y0.domain()[0] and yTrans[1] <= y0.domain()[1]
    if xTransOk
      x.domain xTrans
      successfulTranslate[0] = ev.translate[0]
    if yTransOk
      y.domain yTrans
      successfulTranslate[1] = ev.translate[1]
  zoomer.translate successfulTranslate

graph.select('g.x.axis').call(xAxis)
graph.select('g.y.axis').call(yAxis)
drawBars()

zoomer.on('zoom', onZoom)

# ...
graph.call(zoomer)

Answer 2

You just need to limit the domain on redraw. The following code will prevent the graph from being zoomed out past it's initial domains (as used in http://bl.ocks.org/1182434).

SimpleGraph.prototype.redraw = function() {
  var self = this;
  return function() {

    self.x.domain([Math.max(self.x.domain()[0], self.options.xmin), Math.min(self.x.domain()[1], self.options.xmax)]);

    self.y.domain([Math.max(self.y.domain()[0], self.options.ymin), Math.min(self.y.domain()[1], self.options.ymax)]);

    ....