Talk:Frieze group

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Major tidy-up planned here. The current version is vague and incorrect in several places. Also the list of frieze groups is in a different order to the diagram. The diagram is not explained (the group is not the pattern) nor is it particularly well-chosen, as the friezes come over as noise. I will work on it sporadically over the next hour. --AndrewKepert 06:35, 3 Feb 2004 (UTC)

Okay, getting there. Still some work to do, but it will be dark soon and I haven't yet put lights on my bike for the year. --AndrewKepert 08:15, 3 Feb 2004 (UTC)

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I have finished the overhaul - further tweaking needed. The old image is below: --AndrewKepert 06:50, 9 Feb 2004 (UTC)

The image below gives seven sample patterns on the strip whose symmetry groups are the seven frieze groups. However, the order does not correspond with the order in the list above. (TO FIX)

Contents 1 Comments on recent edits 2 numbering of groups 3 couple of photos 3.1 group 1 3.2 group 2 3.3 group 3 3.4 group 4 3.5 group 5 3.6 group 6 3.7 group 7

[edit] Comments on recent edits

Just for any other observers' benefits, here is a posting I just made to User talk:Patrick:

I noticed that you have contributed a large sequence of edits on Frieze group in the last couple of weeks. Unfortunately your edits have introduced a number of factual errors and problems with the language. I also feel you have introduced too much unnecessary detail, some of which belongs in, or is duplicated in, other articles. Natch. this is all IMHO so take it with 0.0647g of NaCl if you prefer.

Below you mention only one factual error, which I corrected.--Patrick 20:16, 1 August 2005 (UTC)

I will be brief, and use the 1/4/2005 edit of Linas as my point of reference. The side-by-side comparison is here: [1]. My apologies if not all the edits I refer to are yours.

• The opening two sentences are far less clear than the original. In the first, you have made an attempt to refer to the equivalence classes of groups, but the strict mathematical "class of groups of transformations of pairs of numbers" is four levels of abstraction deep (well, five if you consider numbers an abstraction of quantity). Too deep for a general reference work such as WP. IMO the original captures the essence of the groups, and if it is necessary to add the extra level of abstraction, this can be done via a "strictly speaking" comment after the definition, possibly linked to Isomorphism class or whatever. The second sentence is currently incorrect - a group is not an isometry. (Ironically, you have equated an object at one level of the tower of abstraction with one at a different level.)

I moved the formal part a little down and corrected the error. The levels of abstraction are inherent in the subject, I found that leaving one level out was confusing, e.g. a symmetry group of type 2 is only a subgroup of one of type 7 if for the latter we take a smaller translation distance; also combining reflection and rotation is different depending on the positions of the centers, so we can not simply take the origin at the symmetry center.--Patrick 13:10, 1 August 2005 (UTC)

• The introduction of cartesian coordinates is not necessary for the definition of Frieze group, or even the characterisation of the 7 classes. Coords should not be introduced unannounced. However, they are useful in analysing the groups in later sections.

I did not change that.--Patrick 13:18, 1 August 2005 (UTC)

• You have substituted the ° (°) sequence for that symbol in whatever code table your computer and browser likes. It is better to use the character entity. See [2]

It is at the bottom of the edit page, so apparently a Wikimedia standard.--Patrick 13:18, 1 August 2005 (UTC)

• The listing of finite symmetries of a strip is unnecessary detail, amplifying an off-hand remark in the original. Maybe trim back and refer to Point group.

It could be moved there, but since this is specifically about a strip, it is also very much related to the subject of this article.--Patrick 13:24, 1 August 2005 (UTC)

• I am not sure of your intent in the "1D" sections and "Mathematics of ..." sections. I am guessing that you are attempting to demonstrate that these are the only groups by first analysing the action of the group on the long axis and then adding "thickness". However this should be made explicit - the article is not about isometries of R.

I moved the 1D section to a separate article.--Patrick 13:32, 1 August 2005 (UTC)

Finally, a request: "Show preview" and "Comment"! Or at least a brief description of what you are doing and what you plan to do in the talk page. The history page for your edits doesn't help me see what you have done. I don't have time to work on the article just now, and it seems that your are still progressing with your edits. I may visit again in a week or two.

All the best, Andrew Kepert 10:12, 1 August 2005 (UTC)

Hi, I just want to tentatively add my voice to AndrewKepert's comments. Although I'm not familiar with the history of the Frieze group article, I can see there is currently a problem with target audience. At the very least, the introduction to Frieze group should be something along the lines of the introduction Wallpaper group, aimed at a general audience, with all the mathematical terminology separated off in a "formal development" section or something similar. Dmharvey Talk 11:02, 1 August 2005 (UTC)

Good idea, I changed the intro.--Patrick 13:32, 1 August 2005 (UTC)

(following Patrick's intro changes as a result of Andrew's constructive criticism)... I think that's a definite improvement.

Sometime I want to add some real-life photos of these groups occurring in real life, like for what's happening in Wallpaper group. Some time in the next few weeks I'll get around to it hopefully. Having a pretty one in the introduction would be especially illuminating. Dmharvey Talk 16:10, 1 August 2005 (UTC)

[edit] numbering of groups

This numbering by 1, 2, ... 7, is this standard notation? If not, doesn't it add an extra layer of confusion where unnecessary? Dmharvey Talk 10:00, 10 August 2005 (UTC)

[edit] couple of photos

I'm trying to collect some photos to work into this article...

[edit] group 1

[edit] group 2

[edit] group 3

[edit] group 4

[edit] group 5

[edit] group 6

[edit] group 7

Dmharvey 03:07, 12 March 2006 (UTC)