生成节点导纳矩阵，使用MATLAB。

简介：
The function Y is generated based on the provided branch data. If no branch data is supplied as input, it defaults to utilizing the InputData function. The function extracts bus feed (busf) and bus terminal (bust) data, alongside impedance values (z), from the branch data. It determines the total number of branches and the maximum bus number present. Subsequently, a matrix Y is initialized with zeros, possessing dimensions corresponding to the number of branches. The code then iterates through each branch, updating the matrix Y according to a specific calculation: for each branch pair, it subtracts one-third of the impedance value from the corresponding element in Y and adds one-third of the impedance value to that same element. Finally, it ensures symmetry by mirroring this adjustment across the diagonal elements of Y.