Using the stack generator for a waterfall chart?

[mbostock]

For example:

As suggested in https://twitter.com/edouard_lopez/status/682140701707010048.

It might be interesting to think about a better default for stack.keys, too. The current default (empty) is safe, but perhaps this usage pattern suggests a different default expectation for the data and keys.

[mbostock]

Also, this particular example suggests that the stack layout might benefit from allowing negative values, too. (But perhaps it already works out of the box with negative values? Time to find out!)

[mbostock]

I tried this using the stack layout, and I think it’s still overkill. The stack layout expects multiple data points per series, and a waterfall chart only has one data point per series. You can do it, but it feels a lot simpler to just use array.reduce:

// Compute a simple “stack” by iterating over the data.
data.reduce(function(v, d) { return d.value1 = (d.value0 = v) + d.value; }, 0);