Fix Stan syntax error

Author: jgabry

NEWS.md

@@ -17,7 +17,6 @@
 * Update documentation for `E_loo()` function by @avehtari in #312
 
 
-
 # loo 2.8.0
 
 * make E_loo Pareto-k diagnostic more robust by @avehtari in #251

vignettes/loo2-example.Rmd

@@ -61,11 +61,10 @@ models.
 
 ### Roaches data
 
-The example data we'll use comes from Chapter 8.3 of [Gelman and Hill
-(2007)](https://sites.stat.columbia.edu/gelman/arm/). We want to make inferences
-about the efficacy of a certain pest management system at reducing the number of
-roaches in urban apartments. Here is how Gelman and Hill describe the experiment
-and data (pg. 161):
+The example data we'll use comes from Chapter 8.3 of Gelman and Hill (2007). We
+want to make inferences about the efficacy of a certain pest management system
+at reducing the number of roaches in urban apartments. Here is how Gelman and
+Hill describe the experiment and data (pg. 161):
 
 > the treatment and control were applied to 160 and 104 apartments, respectively, and the outcome measurement $y_i$ in each apartment $i$ was the number of roaches caught in a set of traps. Different apartments had traps for different numbers of days
 

vignettes/loo2-moment-matching.Rmd

@@ -68,7 +68,7 @@ data {
   int<lower=1> N;
   matrix[N,K] x;
   array[N] int y;
-  vector[N] offset;
+  vector[N] offset_; // offset is reserved keyword in Stan so use offset_
 
   real beta_prior_scale;
   real alpha_prior_scale;
@@ -78,14 +78,15 @@ parameters {
   real intercept;
 }
 model {
-  y ~ poisson(exp(x * beta + intercept + offset));
+  y ~ poisson(exp(x * beta + intercept + offset_));
   beta ~ normal(0,beta_prior_scale);
   intercept ~ normal(0,alpha_prior_scale);
 }
 generated quantities {
   vector[N] log_lik;
-  for (n in 1:N)
-    log_lik[n] = poisson_lpmf(y[n] | exp(x[n] * beta + intercept + offset[n]));
+  for (n in 1:N) {
+    log_lik[n] = poisson_lpmf(y[n] | exp(x[n] * beta + intercept + offset_[n]));
+  }
 }
 "
 ```
@@ -127,7 +128,7 @@ standata <- list(
   K = k,
   x = as.matrix(x),
   y = y,
-  offset = offset,
+  offset_ = offset,
   beta_prior_scale = 2.5,
   alpha_prior_scale = 5.0
 )