```Path: news.mathworks.com!newsfeed-00.mathworks.com!newsfeed2.dallas1.level3.net!news.level3.com!postnews.google.com!a42g2000vbl.googlegroups.com!not-for-mail
From: Luna Moon <lunamoonmoon@gmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: How do you do this fast?
Date: Fri, 11 Jun 2010 13:26:13 -0700 (PDT)
Lines: 43
NNTP-Posting-Host: 199.89.103.12
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
X-Trace: posting.google.com 1276287973 9035 127.0.0.1 (11 Jun 2010 20:26:13 GMT)
NNTP-Posting-Date: Fri, 11 Jun 2010 20:26:13 +0000 (UTC)
posting-account=CYtergoAAAAOD8k-T_NdzknPJOBXmt8x
User-Agent: G2/1.0
X-HTTP-Via: 1.1 piinbcgw03
X-HTTP-UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3)
Gecko/2010041205 Firefox/3.6.3ms1,gzip(gfe)
Xref: news.mathworks.com comp.soft-sys.matlab:644265

Hi all,

I have sets A, B, C, where C is the biggest set, A is the smallest,

C>B>A, i.e. C contains B contains A.

These are indices indeed.

I have a matrix m x n matrix MatrixC, where C=[1:n].

I have created a matrix MatrixB, which is

MatrixB=MatrixC(:, B).

Now I want to obtain MatrixA, which is

MatrixA=MatrixC(:, A).

---------------------------

However, in reality, actually for cost reasons, I didn't measure all
MatrixC,

instead, I took measurements for MatrixB.

So all I have now is MatrixB, and sets A, B, C.

i.e. the indices A and B are "in C's language".

i.e. the indices A and B are numbered according to their positions in
C=[1:n].

So the question is:

how do I obtain MatrixA from MatrixB and sets A, B, C?

I currently use a "for" loop plus "find" etc. to do this job,

are there any fast approach without using "for" and "find"?

Mine is too slow... too stupid...

Thank you!
```