large numbers in K means

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Tino
Tino on 15 Jun 2019
Commented: John D'Errico on 15 Jun 2019
I am trying to find the kmeans of 1 column with 1048575 numbers rows
and I am getting the error below
Error using kmeans (line 277)
X must have more rows than the number of clusters.
Error in svia (line 18)
[idx, C, miro , D] = kmeans(bibi, K);
Can anyone assist me in finding a solution for this.
Thanks in advance
Tino

Accepted Answer

Guillaume
Guillaume on 15 Jun 2019
What's unclear about the error? You must specify less cluster than the number of rows in your matrix/vector. So make sure that K is less than size(bibi, 1) (or numel(bibi) if a vector).
  2 Comments
Walter Roberson
Walter Roberson on 15 Jun 2019
It would be a problem for kmeans if bibi is a row vector instead of a column vector.
Guillaume
Guillaume on 15 Jun 2019
Not according to the doc: "If X is a numeric vector, then kmeans treats it as an n-by-1 data matrix, regardless of its orientation."

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More Answers (1)

John D'Errico
John D'Errico on 15 Jun 2019
Edited: John D'Errico on 15 Jun 2019
x = rand(1048575,1);
size(x)
ans =
1048575 1
[IDX, C] = kmeans(x, 10);
C
Warning: Failed to converge in 100 iterations.
> In kmeans/loopBody (line 479)
In internal.stats.parallel.smartForReduce (line 136)
In kmeans (line 343)
C =
0.74809
0.049586
0.94968
0.2486
0.54773
0.64779
0.34794
0.14901
0.44755
0.84915
It works fine, athough It seems starved for iterations. But that is trivially solved.
However, if I make a mistake, and pass in a ROW vector instead, then I get the same error that you did.
[IDX, C] = kmeans(x', 10);
Error using kmeans (line 277)
X must have more rows than the number of clusters.
  2 Comments
Guillaume
Guillaume on 15 Jun 2019
That's countrary to the documentation which says: "If X is a numeric vector, then kmeans treats it as an n-by-1 data matrix, regardless of its orientation".
I don't have the required toolbox but if that's not what happens then it should be reported as a bug.
John D'Errico
John D'Errico on 15 Jun 2019
That is indeed the statement, in R2019a. So it is indeed a bug, since the behavior runs contrary to the documentation.

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