I am learning about non parametric estimation, and more specifically about regressogram:
Let $(X_i,Y_i)_{i = 1}^n$ be a sequence of random variables in $[0,1]$ variables and $E[Y_i|X_i] = f(X_i)$. Let $I_1,\dots,I_K$ be the regular partition of the unit interval. Suppose $x\in I_k$, then $$\hat{f}_n(x) = \frac{\sum_{i=1}^nY_i1(X_i\in I_k)}{\sum_{i=1}^n1(X_i\in I_k)}.$$
I would like to know how to control the error $|\hat{f}_n(x)-f(x)|$? Is there a reference?