Incorrect derivative of function w.r.t. parameterized argument alpha

[bentyeh]

This footnote is not quite right.

post--attribution-baselines/public/index.html

Lines 267 to 278 in 765dadd

	<d-footnote>That is, if we integrate over the
	straight-line between \(x'\) and \(x\), which
	we can represent as \(\gamma(\alpha) =
	x' + \alpha(x - x')\), then:
	$$
	\frac{\delta f(\gamma(\alpha))}{\delta \alpha} =
	\frac{\delta f(\gamma(\alpha))}{\delta \gamma(\alpha)} \times
	\frac{\delta \gamma(\alpha)}{\delta \alpha} =
	\frac{\delta f(x' + \alpha' (x - x'))}{\delta x_i} \times (x_i - x'_i)
	$$
	The difference from baseline term is the derivative of the
	path function \(\gamma\) with respect to \(\alpha\).

$$\gamma(\alpha)$$ is a vector, so by the multivariable chain rule,

$$
\frac{\delta f(\gamma(\alpha))}{\delta \alpha}
= \sum_i \frac{\delta f(\gamma(\alpha))}{\delta \gamma_i} \times  
  \frac{\delta \gamma_i(\alpha)}{\delta \alpha}
= \sum_i \frac{\delta f(x' + \alpha' (x - x'))}{\delta x_i} \times (x_i - x'_i)
$$

[psturmfels]

You are right! That footnote definitely contains errors, and your version is correct. I'm happy to change this myself, but also happy to accept a pull request. Either way, I'll try and update it this evening. Thank you for spotting this!

[bentyeh]

I created a pull request: #6