# Pivoting posteriors

In Stan, when a parameter is declared as an array, the samples/draws data frame will have columns that use the [i] notation to denote the i-th element of the array. For example, suppose we had a model with two parameters – (\lambda_1) and a (\lambda_2). Instead of declaring them individually – e.g. lambda1 and lambda2, respectively – we may declare them as a single lambda array of size 2: parameters { real lambda[2]; } When we sample from that model, we will end up with samples for lambda[1] and lambda[2].