log-log relationship.

[Ender]

Once again I turn to this place to answer the questions generated by my limited knowledge...

When I wrote Dr. Saxton, he said he assumed there was a log-log relationship between reactor volume and reactor power. Now I went in and I checked every last T manual I was issued. I went to the learning resource center (library) and did a search. I asked instructors. No one could tell me what it means. Closest I can come is that start up rate is displayed on a log scale because otherwise it would be too large, but that doesn't fit. I wrote the good doctor for clarification and also emailed the DoE, but I am yet to get a response from either.

So what is a log log relationship? Can someone provide an example of one that I could try and figure out the exact one used by Saxton?

Thank you.

[Warspite]

You know what a logarithmic expression is, right? You know the general shape of the log function, yes?

OK, so, when you plot reactor volume versus reactor power in a log-log chart, that is, a chart where both axis are in a logarithmic scale (easy to do in Excell for example), you get a straight line of values, hence log-log relationship, in other words, they are directly related by a logarithmic function.

Close enough?

[Ender]

Much, thank you.

http://bbs.stardestroyer.net/viewtopic.php?t=22268

But how do you graph it in Excell? I am having difficulty getting that program to work.

[Warspite]

The main problem with logarithmic scales (in general) is, they are based in powers of 10, that is, the main lines are in multiples of ten, so unless the values are spread over several orders of magnitude, there wont be much to see, except for a lump of points.

In Excell, these are the steps to plot a table of values in a logarithmic scale:

Choose the scatter plot, give all the preferences you whish, finish, then, over the axis lines, click the RMB (right mouse button), format axis, scale tab, at the bottom there will be a check box marked logarithmic scale.


Still, very strange results... with which values are you ploting?

[Kuroneko]

I went to the learning resource center (library) and did a search. I asked instructors. No one could tell me what it means...

I'm suprised to hear that; I didn't think the phrase "log-log relationship" was that uncommon in mathematics. Well, usually I see it as "log-linear", so I assume what was meant there is simply that. x in a linear log-linear relationship with y just means log(y) = a log(x) + b.

As Warspite already said, it's simply an artificial transformation to make both scales logarithmic in order to deal with data over very large ranges.