I am trying to convert some custom matrix and vector classes to Eigen for speed/vectorization. I don't understand how to write code with minimal overhead to 1-index into Eigen classes, maintaining all the optimizations from expression templates and SSE. Currently, I am inheriting from Matrix and writing my own operator() functions in a wrapper class, but then things such as directly indexing into CWiseBinaryOp are off by one and cause errors. Is there any elegant way to fix this? Unfortunately, 0-indexing the code is not an option. TIA