Hi Stan community,

I have a question about how to write the likelihood in the Stan code when there are repeated measurement in a timeseries. The timeseries is N datapoints long, and I have two columns, one for the first measurement and another for the second measurement. There are also predictors, which I don’t show here. I wonder if it works to write the likelihood twice (as in the below Stan-code), or if I should first gather the data into groups of measurements and then write the likelihood so that it loops first through measurements then through observations.

Thank you for the help.

```
data {
int<lower=0> N; // number of datapoints
real[N] y1; // first measurement for each datapoint
real[N] y2; // second measurement for each datapoint
}
parameters {
real mu[N]; //
real<lower=0> sigma;
}
model {
for (i in 1:N) {
y1[i] ~ normal(mu[i], sigma);
y2[i] ~ normal(mu[i], sigma);
}
}
```