diff --git a/_tests/pdf-include-in-header.qmd b/_tests/pdf-include-in-header.qmd index 0a1241e..585a611 100644 --- a/_tests/pdf-include-in-header.qmd +++ b/_tests/pdf-include-in-header.qmd @@ -39,6 +39,8 @@ Sum of the elements, plain, squared and with a tall argument: $\sumof{\vy}$, $\S Fitted prediction function, plain, squared and applied: $\epredfn^2$, $\epredfnf{x}^2$, $\predfnf{x}_i$, $\bestpredfnf{x}^2$. +Conditional risk, plain, squared, subscripted and with a tall argument: $\condpopriskf{\modmem}{x}$, $\condpopriskf{\modmem}{x}^2$, $\condpopriskf{\modmem}{x}_i$, $\condpopriskf{\modmem}{\frac{a}{b}}^2$. + Sample means, plain, subscripted and squared: $\smean{y}_i^2$, $\xbar^2$, $\samplemean{X}{n}^2$, $\smeandev^2$, $\smeandev_i$, $\avgleverage^2$. Sums of squares, squared and subscripted: $\RSS^2$, $\RSS_0$, $\TSS_i$. Training symbols: $\nnetparams^2$, $\iter_i$, $\layeridx^2$, $\objfn_i$, $\objfnf{\vth}^2$. diff --git a/interpretations.tsv b/interpretations.tsv index 2f26aae..15ebc0b 100644 --- a/interpretations.tsv +++ b/interpretations.tsv @@ -172,6 +172,7 @@ name interpretation \obsloss loss on one observation, ℓ_i (argument: the observation index) \poprisk population (true) risk symbol R: the expected loss of a model \popriskf population risk of a model, R(·) +\condpopriskf conditional (pointwise) risk of a model at an input, R(f | x): the expected loss given the input; its average over the input is the population risk \lpnorm name of an ℓ_p norm or penalty, such as ℓ_1 or ℓ_2 (argument: p) \lbound a lower bound of a set (ℓ) \ubound an upper bound of a set (u) diff --git a/macros.qmd b/macros.qmd index 5ec855b..159b53d 100644 --- a/macros.qmd +++ b/macros.qmd @@ -183,6 +183,7 @@ \providecommand{\obsloss}[1]{\ell_{#1}} \def\poprisk{R} \providecommand{\popriskf}[1]{{\poprisk\paren{#1}}} +\providecommand{\condpopriskf}[2]{{\poprisk\paren{#1 \mid #2}}} \def\modelfam{\mathcal{H}} \def\growthfn{m_{\predfam}} \providecommand{\growthfnf}[1]{{\growthfn\paren{#1}}} diff --git a/notation-choices.qmd b/notation-choices.qmd index 4b4e5dd..de2053c 100644 --- a/notation-choices.qmd +++ b/notation-choices.qmd @@ -330,6 +330,11 @@ We write the expectation, the probability, the bias and the variance as operator The blackboard letter marks an operator that takes a random variable or an estimator, so it cannot be mistaken for an italic variable. We do not use blackboard bold for the risk, because $\reals$ is the real numbers. The risk stays an italic $\poprisk$, which is free now that the noise is $\varepsilon$. +The risk of a model at one input, the conditional risk, is the same italic letter with the input after a bar: $\condpopriskf{\modmem}{x}$. +We keep one letter for both because they are one quantity at two levels. +The population risk $\popriskf{\modmem}$ is the average of $\condpopriskf{\modmem}{\predvar}$ over the distribution of the input. +Duda and Hart make the same split, between the conditional risk and the overall risk, and *The Elements of Statistical Learning* writes the pointwise form $\mathrm{EPE}(x_0)$ beside $\mathrm{EPE}(f)$. +*An Introduction to Statistical Learning* does not separate them. The long operators $\Biast$ and $\Vart$ stay upright words. We make this exception to the Greek convention for estimands in [the estimands entry](#sec-estimand-estimator-symbols). The variance operator applies to any random variable, not only to a fitted value.