i’m building a standard linear regression model and i want to include the `generated quantities`

block and i want to use the `dot_self()`

function. The problem is I can´t get simulation samples. The error is: `Stan model 'LinearRegression' does not contain samples.`

. I think the the function `dot_self()`

is not being recognized as a function. I show `stan`

code and `R`

code here. Thanks in advance.

Note: I am sure that the data entered is correct because the model without the `generated quantities`

block works perfectly.

STAN CODE

```
data {
int<lower=1> N;
int<lower=1> K;
matrix[N, K] X;
vector[N] y;
}
parameters {
vector[K] beta;
real<lower=0> sigma;
}
model{
vector[N] mu;
mu = X * beta;
beta ~ normal(0, 10);
sigma ~ cauchy(0, 5);
y ~ normal(mu, sigma);
}
generated quantities {
real rss;
real totalss;
real<lower=0, upper=1> R2;
vector[N] mu;
mu=X * beta;
rss=dot_self(y-mu);
totalss=dot_self(y-mean(y));
R2=1 - rss/totalss;
}
```

R CODE

```
library(rstan)
library(coda)
library(ggplot2)
rstan_options(auto_write=T)
options(mc.cores=parallel::detectCores())
dat=list(N=N, K=ncol(X), y=y, X=X)
fit3 = stan(file = "C:.... LinearRegression.stan", data = dat, iter = 100,chains = 4)
print(fit3, digits=3, prob=c(.025,.5,.975))
```