思路：将要删除的某行、某列后边的数据以块的形式，移动到要删除的某行、某列上。
删除矩阵某一行：
void RemoveRow(Eigen::Matrix3Xd& matrix, unsigned int rowToRemove) { unsigned int numRows = matrix.rows() - 1; unsigned int numCols = matrix.cols(); if( rowToRemove < numRows ) { matrix.block(rowToRemove,0,numRows-rowToRemove,numCols) = matrix.block(rowToRemove+1,0,numRows-rowToRemove,numCols); } matrix.conservativeResize(numRows,numCols); }删除矩阵某一列：
void RemoveColumn(Eigen::Matrix3Xd& matrix, unsigned int colToRemove) { unsigned int numRows = matrix.rows(); unsigned int numCols = matrix.cols() - 1; if( colToRemove < numCols ) { matrix.block(0, colToRemove, numRows, numCols - colToRemove) = matrix.block(0, colToRemove + 1, numRows, numCols - colToRemove); } matrix.conservativeResize(numRows,numCols); }转自：https://blog.csdn.net/zkangsen/article/details/95756365
