Error in t(da) %*% da : requires numeric/complex matrix/vector arguments
To get the matrix multiplication to work, you need to convert the data.frame (presumably that's what da is) to a matrix:
But this gives a 7x7 matrix which can't be added to the 3x3 identity matrix that you're using. Do you mean something like:
You may like to have a look at An Introduction to R if you don't feel confident about the difference between a matrix and data.frame.