Rank: 2954 based on 44 downloads (last 30 days) and 3 files submitted
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Kardi Teknomo

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Files Posted by Kardi Teknomo View all
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03 Nov 2010 Mahalanobis Distance Return mahalanobis distance of two data matrices A and B (row = object, column = feature) Author: Kardi Teknomo mahalanobis distance, statistics, data mining, pattern recognition, distance, chava 16 0
03 Nov 2010 Covariance matrix Return covariance matrix for given data matrix X (row = object, column = feature) Author: Kardi Teknomo statistics, distance, data mining 7 2
  • 1.0
1.0 | 2 ratings
29 Sep 2006 VLOOKUP vlookup tutorial Author: Kardi Teknomo matrices, lookup table, vlookup 21 3
  • 3.0
3.0 | 3 ratings
Comments and Ratings on Kardi Teknomo's Files View all
Updated File Comment by Comments Rating
16 Apr 2013 Covariance matrix Return covariance matrix for given data matrix X (row = object, column = feature) Author: Kardi Teknomo John D'Errico

This is not badly written. It does use array operations to do the job. It does have some meager help, although not an H1 line.

The problem is that an existing code already exists in MATLAB, that is faster, better written, with better help, and more options.

X = randn(1000000,10);
timeit(@() Covariance(X))
ans =
0.1096

timeit(@() cov(X))
ans =
0.0771

X = randn(100000,3);
timeit(@() cov(X))
ans =
0.0012

timeit(@() Covariance(X))
ans =
0.0035

16 Apr 2013 Covariance matrix Return covariance matrix for given data matrix X (row = object, column = feature) Author: Kardi Teknomo seongjin

Using MatlabR2012.
Built-in function cov(X,1) does the same calculation, and it is faster.

Try the following code.

x = randn(400000,100);

tic
c1 = Covariance(x);
toc

tic
c2 = cov(x,1);
toc

16 Apr 2013 Covariance matrix Return covariance matrix for given data matrix X (row = object, column = feature) Author: Kardi Teknomo seongjin

16 Mar 2008 VLOOKUP vlookup tutorial Author: Kardi Teknomo

I agree with Jeff. Have to be very careful since the function does not give the exact match.

10 Jul 2007 VLOOKUP vlookup tutorial Author: Kardi Teknomo

comment pouvant savoir ? quelle couleur correspond une valeur de pixel

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