# Linear to logarithmic scale conversion

1. Feb 27, 2010

### jocasa

Hi!

I'm making a computer program that represents some quantities in a graph in this way:

x'i=(xi-xmin)/(xmax-xmin)

so that the possible values of x range from 0 to 1. This is a linear scale. I want to do the same with the logarithmic values of xi. That is, I want to implement a log scale in my graphs, also in the range from 0 to 1.

Can anyone tell me how to do it?

Thanks!

2. Feb 27, 2010

### Staff: Mentor

Welcome to the PF.

What language are you programming in? Does it have any math libraries that cover logarithms?

3. Feb 28, 2010

### jocasa

I'm not sure if I made myself clear in my first post. I want to be able to make log-log plots, transforming the resulting plot into the [0,1] interval.

4. Feb 28, 2010

### Redbelly98

Staff Emeritus
I think this will work:

x'i = (log(xi)-log(xmin)) / (log(xmax)-log(xmin))​
As a test, we can see that if xmin,max are 1 and 100, then xi=10 gives x'i=0.5. As it should, since 10 is halfway between 1 and 100 on a log scale.

5. Feb 28, 2010

### jocasa

Thanks! It makes sense to me. Now the problem is to implement it in the program, but I won't bother you with such a thing. Thanks again from Spain!