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What do brackets mean after a type is specified when declaring variables in Stan?

I saw a Stan program where the data block contained int person[N_obs]. Is this creating an array of integers of size N_obs that is called with person?

Solution

  • Yes, exactly. Brackets behind the variable names specify an array of the type that was specified before the name. In addition, for collection data types like vector and matrix, you need to specify the size behind the data type:

    vector[N] y;
matrix[N, K] X;

    You can also create arrays of collection data types. For example

    vector[N] X[K];

    would specify an array of K vectors of size N.