# Graphing a log

• Nov 15th 2007, 03:20 AM
daragh8008
Graphing a log
Hi all,
just a quick question about logs and graphs. I have a graph of two variables log of f and and log of R with logR being on the x axis. The graph forms a straight line with an equation of the form y=mc+c. There is a relationship between f and R of the form f=KR^a. How would one go aboout finding the values of K and a from the graph. Any pointers would be greatly appreciated.

Thanks
• Nov 15th 2007, 06:06 AM
topsquark
Quote:

Originally Posted by daragh8008
Hi all,
just a quick question about logs and graphs. I have a graph of two variables log of f and and log of R with logR being on the x axis. The graph forms a straight line with an equation of the form y=mc+c. There is a relationship between f and R of the form f=KR^a. How would one go aboout finding the values of K and a from the graph. Any pointers would be greatly appreciated.

Thanks

I take it you are graphing log(R) vs. log(f), then? Well, if the relationship between the two variables is
$\displaystyle f = KR^a$

$\displaystyle log(f) = log(KR^a)$

$\displaystyle log(f) = log(R^a) + log(K)$

$\displaystyle log(f) = a \cdot log(R) + log(K)$

This is in the form of a line (y = mx + b), where the slope is a and the intercept is log(K).

-Dan
• Nov 15th 2007, 08:04 AM
daragh8008
Many thanks. Might stand a chance of finding the solution now:)

Thanks again