It's very good, but suffers from one basic presentational error: You've placed Republicans on the left and Democrats on the right. While I know your algorithm doesn't attempt to plot people on a particular spectrum, it so happens that stereotypically partisan conservative or liberal senators tend to be positioned at the outer margins anyway. since liberals are traditionally thought of as left-leaning and conservatives as right-leaning [1], I would suggest your diagram needs to be flipped horizontally.

1. http://en.wikipedia.org/wiki/Left%E2%80%93right_politics#His...

The visualization is totally cool, though I don't claim to understand the analysis.

...but if it helps, you made a little English error. Wouldn't even have mentioned if you hadn't said you were French :)

> [Republicans.] Most of which are either moderates or closer to the Democrats than to their own party.

> Olympia Snowe and Susan Collins are the two Republican Senators from Maine which are both regarded to be leading moderates within their party.

Should be "Most of whom..." and "...who are both...".

"Which" is only ever[1] used in relative clauses to describe inanimate objects (as you do correctly five other times in the article). Humans and animals are always either "who" (more personal) or "that" (more impersonal).

Note that's only in relative clauses-- "Which senator is yours?" is fine, but "The senator which represents me" means that I think my senator is a card table.[2]

[1] Outside of the odd dialect, of course.

[2] Not necessarily out of the question.

You're perfectly right, I've reworked the text several times and these mistake slipped through the proofreading. Thanks for pointing them out.

I'll assume you're correct in your explanation. I've never heard it explained that way.

But as a native speaker "that" sounds slightly more correct than "which" because it seems less formal, however, if I heard a non-native speaker say "which" it wouldn't sound weird nor would it be something I would have corrected them on.

In American English, which is normally used in non-restrictive clauses (offset by commas), and that is normally used in restrictive clauses (not offset by commas).

Using which in a restrictive clause like The senator which represents me... or The road which runs from X to Y... is somewhat uncommon. Both of those examples sound better in American English using that in place of which. If the subjects didn't need disambiguation, though, that would no longer be appropriate, e.g., Senator Jones, who represents me, ... or Foobar Street, which runs from X to Y, ...

As Cushman points out, though, which used on a person doesn't quite work. That can work on a person, though, but who/whom can work for people in both restrictive and non-restrictive clauses.

See http://owl.english.purdue.edu/owl/resource/645/01/ if you want to read a well-structured and thorough explanation.

Of course, with all of this stuff, people have different sensitivities-- and I know there are some dialects where "which" regularly references a person. I actually might not notice the first occurrence myself, although on reflection it looks a little odd. The second one jumped out at me as seeming pretty weird, though.

Even so, I wouldn't correct it except that, read uncharitably, referring to a person with an inanimate term could be seen as somewhat insulting. Especially if you're writing about politics, it's probably worth getting right just to avoid that impression.

Which sets of Senators were facing election that year? As a rule, only approximately a third. It would be nice to see if they were correlated to the group "switching" sides.

Which party controlled the Senate that year? It would be interesting to see if switching is correlated to party control. For instance, I see the Republicans controlled the Senate in the 108th (2003-2004).

Thanks for the idea, I didn't think of the reelection aspects, I'll investigate.

> One unexplicable point remains in the data and that is the presence of 18 Democrats in the Republican group of the 108th Congress.

Dude, check the dates. Two words: Iraq invasion.

I thought about that, but 12 of the 18 Democrats were fiercely opposed to the invasion…

Which ones? All the ones I click seem to be in favour :)

Regardless, they might have voted against the operation but then voted for various smaller bills "supporting the troops", which is an entirely reasonable position.

I'll have to go back to my notes, but I'm pretty sure I found a lot of opponents, but maybe I'm remembering wrong. Thank for pointing this out, I'll have another closer look !

The lead up to the war was very much "you're either with us or against us". It took a lot of courage to speak against the war. Even the media had to get in line - I think all news networks hired military consultants at the time.

Over time some that voted for invasion adjusted their stance. This may be why you felt there were a lot of opponents.

Typo in the Hagel quote: it's "almost every area", not "almost every are".