# condition number

• February 27th 2009, 09:04 AM
PvtBillPilgrim
condition number
The relative condition number is defined here:
Numerical Linear Algebra - Google Book Search

In an example, I have that f(x) = exp(x). What is the relative condition number here?

I assume it is x*exp(x)/exp(x) = x. Is this correct?
• February 27th 2009, 03:28 PM
HallsofIvy
Well, the site you link to gives the "relative condition number" as $\frac{||J||||x||}{||f(x)||}$ and further notes that if f is a real valued function of a single real variable, that reduces to $\frac{|f'(x)||x|}{|f(x)|}$. In your example, f(x)= exp(x), f'(x) is also exp(x) so they cancel and your are almost correct- the relative condition number is |x|.