Sometimes we will either want to store information in a matrix as opposed to as a variable (“gen”). Other times we may want to manipulate a matrix. Two types of matrices within Stata Stata matrix, this is limited by the version of Stata you have. Is an older feature of Stata. All commands start with “matrix”. Mata matrix, this is only limited by the physical hardware of your computer. Used in the mata environment, or commands start with “mata: ” Can initialize a matrix with J(r,c,.) for a “blank” matrix, J(r,c,0) for a matrix of zeros, and J(r,c,1) for a matrix of ones. Initializing matrices with “.” as a place holder will help you to catch errors in your code.