eigen: Subtracting a scalar from a vector

The simplest is to move to the so called "array" world:

VECTOR_TYPE test = singular_values.array() - offset;

It's mathematically invalid to subtract a scalar (which is just a one-dimensional vector) from a vector, so Eigen correctly throws an error.

Instead, you should write

auto n = singular_values.size();
VECTOR_TYPE test = singular_values - offset * VECTOR_TYPE::Ones(n);

Moreover, you can have a look at the array() functionality which provides element-wise transformations.