I'm working on learning more about logistic regression and I came across an equation with some confusing notation that I've never seen before:
$$ \frac{\delta}{\delta \theta_{y'}^{(j)}} l(\theta) = \sum^N_{n=1} \left[ [y_n = y'] x_n^{(j)} - p(y' | x_n) x_n^{(j)} \right] $$
The part that is unclear is the $[y_n = y']$. Is this just supposed to be a sort of if statement in mathematics?
Something like, "only process the following if this constraint holds true"?
Any clarification would be appreciated. Thanks!
That's probably an Iverson bracket.