Hi everyone, I currently have trouble executing the below stan model, but I could not detect why it keeps giving me this error message in order to fix my code. Could someone please help me resolve this issue? I got stuck on this problem for a couple of months already:((

“Error in new_CppObject_xp(fields$.module, fields$.pointer, …) :

mismatch in dimension declared and found in context; processing stage=data initialization; variable name=epsilon; position=0; dims declared=(16); dims found=(24)”

**Stan Model, saved as stamodeling.stan"**

```
data {
int<lower=1> ncol;
int<lower=1> nrow;
vector[ncol] yH;
matrix[nrow, ncol] A;
vector[ncol] sigma_x;
vector[ncol] sigma_y;
vector[nrow] epsilon;
}
parameters {
vector[ncol] yT;
}
model {
vector[nrow] xT;
vector[nrow] x;
//priors
yT ~ normal(yH, sigma_y);
#xT = A*yT + epsilon; //creation of linear constraint
//likelihood
x ~ normal(A*yT+epsilon, sigma_x);
}
```

**Execution in R**

rstan_options(auto_write = TRUE)

library(rstan)

library(MASS)

library(truncnorm)

```
nrow = 16;
ncol = 24;
iterations = 50000;
A <- matrix(c(1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_A^1 - Done
0,0,0,1,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_A^2 - Done
0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_B^1 - Done
1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_B^2 - Done
0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_C^1 - Done
0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0, #x_C^2 - Done
0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0, #x_D^1 - Done
0,0,1,0,0,1,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, #x_D^2 - Done
0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0, #x_E^1 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,1,0, #x_E^2 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0, #x_F^1 - Done
0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,1,0,0, #x_F^2 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,1,0,0,1,0,0,0,0, #x_G^2 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1, #x_G^1 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0, #x_H^1 - Done
0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,1,0,0,1), #x_H^2 - Done
nrow, ncol, byrow= TRUE);
lambda = array(sample.int(100, size = ncol, replace = TRUE),ncol);
yH <- rtruncnorm(ncol,a = 0, b = lambda+1, mean = 0, sd = 1);
sigma_x <- array(0.2, ncol);
sigma_y <- array(0.3, ncol);
epsilon <- array(0.1, ncol);
stanmodel1 <- stan_model(file = "stamodeling.stan",
model_name = "stanmodel1");
stanfit <- sampling(stanmodel1, data = list(ncol = ncol,nrow = nrow,
yH = yH,
A = A, sigma_x = sigma_x, sigma_y = sigma_y, epsilon = epsilon)
,iter=iterations, warmup = 1000, chains = 3, cores = 1);
```

A follow-up question: If I want to use MCMC as a sampling method, how does the syntax for `stanfit`

change?