The function is given by \( f(x) = x^2 - 2ax + b \). To find the values of \( a \) for which \( f(x) \) is increasing for \( x>0 \), we compute its first derivative and apply the condition for an increasing function.
The first derivative is \( f'(x) = 2x - 2a \).
For \( f(x) \) to be increasing for \( x>0 \), we require \( f'(x) \geq 0 \) for all \( x>0 \).
This means \( 2x - 2a \geq 0 \) for \( x>0 \).
Simplifying, we get \( x \geq a \) for \( x>0 \).
This inequality holds for all \( x>0 \) if and only if \( a \leq 0 \).
Therefore, the function \( f(x) \) is increasing for \( x>0 \) when \( a \leq 0 \). The set of values for \( a \) is \( \boxed{a \leq 0} \).