I am new to R and also using stan modelling. I keep getting this error that my variable doesn’t exist

// Bayesian logistic regression model in Stan

data {

int<lower=0> N; // Number of observations

int<lower=0, upper=1> y[N]; // Binary outcome variable

real age[N]; // Age variable

int<lower=0, upper=1> sex[N]; // Sex variable

int<lower=0, upper=3> cp[N]; // Chest pain type variable

real trestbps[N]; // Resting blood pressure variable

real chol[N]; // Cholesterol variable

real thalch[N]; // Maximum heart rate achieved variable

}

parameters {

real alpha; // Intercept

real beta_age; // Coefficient for age

real beta_sex; // Coefficient for sex

vector[3] beta_cp; // Coefficients for chest pain type (3 dummy variables)

real beta_trestbps; // Coefficient for resting blood pressure

real beta_chol; // Coefficient for cholesterol

real beta_thalch; // Coefficient for maximum heart rate achieved

}

model {

// Priors

alpha ~ normal(0, 1); // Noninformative prior for intercept

beta_age ~ normal(0, 1); // Noninformative prior for age coefficient

beta_sex ~ normal(0, 1); // Noninformative prior for sex coefficient

beta_cp ~ normal(0, 1); // Noninformative prior for coefficients of chest pain type

beta_trestbps ~ normal(0, 1); // Noninformative prior for resting blood pressure coefficient

beta_chol ~ normal(0, 1); // Noninformative prior for cholesterol coefficient

beta_thalch ~ normal(0, 1); // Noninformative prior for maximum heart rate coefficient

// Likelihood

for (i in 1:N) {

real linpred;

linpred = alpha + beta_age * age[i] + beta_sex * sex[i] + beta_cp[cp[i]] + beta_trestbps * trestbps[i] + beta_chol * chol[i] + beta_thalch * thalch[i];

y[i] ~ bernoulli_logit(linpred);

}

}

and

data_list ← list(

N = nrow(train_data),

y = train_data$binary_num,

age = train_data$age,

sex = train_data$sex,

cp = train_data$cp,

trestbps = train_data$trestbps,

chol = train_data$chol,

thalch = train_data$thalch

)

# Compile the Stan model

stan_model ← stan(file = “bayeslrm.stan”)

Anyone that could help me with this, Im really struggling. Thank you!