In regression problems, the label space $\mathbf{Y}$ is the set of real numbers, $\mathbf{Y}=\mathbb{R}$ (sometimes, a connected subset of $\mathbb{R}$, such as ${[0,\infty)}$ or ${[0,1]}$). Allowed forecasts in such problems are elements of $\mathbf{Y}$ (we will have a probabilistic regression problem if we allow probability measures on $\mathbf{Y}$ as forecasts).