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Re: problem plotting "N-d object"
From: |
Sergei Steshenko |
Subject: |
Re: problem plotting "N-d object" |
Date: |
Fri, 17 Feb 2012 10:35:37 -0800 (PST) |
>________________________________
> From: James Sherman Jr. <address@hidden>
>To: Sergei Steshenko <address@hidden>
>Cc: Ben Abbott <address@hidden>; "address@hidden" <address@hidden>
>Sent: Friday, February 17, 2012 7:13 PM
>Subject: Re: problem plotting "N-d object"
>
>
>Because of my math background I find it senseless to say that a 3-d cube
>projection onto a 2-d plane is still 3-d - it is just 2-d, and, likewise, that
>2-d cube image of a cube on a plane being projected onto a 1-d straight line
>would be just 1-d.
>
>This isn't even a solid mathematical reason. The image of a cube on a 2-d
>plane in R^3 is different than the image of a cube in R^2. Or, in otherwords,
>the matrix transformations defined by the matrices A = [1 0 0;0 1 0;0 0 0] and
>A = [1 0 0;0 1 0] are different transformations (they have different codomains
>for one).
>
>
>But, I'd agree that for something like the plot function, it would make sense
>to apply squeeze ahead of time (I certainly can't think of any case where it'd
>make sense to not do squeeze), and for many projects, I have actually written
>a small wrapper around plot that does exactly that (and some otherstuff).
>
>
>But like Ben mentioned, its hard to anticipate where this may not prove
>useful, and probably would be best on a case-by-case basis to do something
>like this.
>
>
>Thats my 2 cents.
>
>
>James Sherman
>
>
I meant my high school geometry background.
Anyway, in 'octave':
"
octave:11> foo = [1 2 3; 4 5 6]
foo =
1 2 3
4 5 6
octave:12> size(foo(:, 1))
ans =
2 1
octave:13> size(foo(1, :))
ans =
1 3
octave:14> isvector(foo(:, 1))
ans = 1
octave:15> isvector(foo(1, :))
ans = 1
octave:16>
".
My point is that an originally 2-d object with any one of the two indexes
fixed/constant is perceived by 'octave' as 1-d object - either as row or column
vector, but as _vector_. Exactly as I expect.
And that's why I expected from 'octave' to perceive an originally 3-d object
with two fixed/constant indexes as 1-d vector. Probably as a column one because
I feel that overall 'octave' is friendlier to column vectors.
Thanks,
Sergei.
- Re: problem plotting "N-d object", (continued)
- Re: problem plotting "N-d object", Pascal A. Dupuis, 2012/02/20
- Re: problem plotting "N-d object", Jordi Gutiérrez Hermoso, 2012/02/20
- Re: problem plotting "N-d object", Pascal A. Dupuis, 2012/02/20
- Re: problem plotting "N-d object", Ben Abbott, 2012/02/20
- Re: problem plotting "N-d object", CdeMills, 2012/02/21
- Re: problem plotting "N-d object", Ben Abbott, 2012/02/21
- Re: problem plotting "N-d object", Sergei Steshenko, 2012/02/21
- Re: problem plotting "N-d object", Ben Abbott, 2012/02/17
- Re: problem plotting "N-d object", Ben Abbott, 2012/02/18
- Re: problem plotting "N-d object", James Sherman Jr., 2012/02/17
- Re: problem plotting "N-d object",
Sergei Steshenko <=