For matrices, mean (X) is a rowvector containing the mean value of each column.
对于矩阵来说,MEAN (X)是包含了每列平均值的行向量。
2
Then for each row from the fact table scan, the foreign key is also hashed and probed into the bit vector to determine whether the current fact table row is filtered out.
然后针对事实表扫描的每一行,外键也被散列并探测到位向量中,从而判断当前的事实表行是否被过滤掉了。
3
One thing that can be confusing about R's "everything is a vector" approach is that row-wise and column-wise operations may not adhere to your intuition.