Machine learning program question

The program I'm asking my question about is in that link: http://read.pudn.com/downloads197/sourcecode/macos/928928/CancerDiagnosis.m__.htm

Now, what does this command do exactly:

testmat= matrix(idtest,:);

and why it's not giving this error:

 Subscript indices must either be real positive integers or logicals.

[CHANDRU G]

x=x+3; data.Xval=data.Xval +3; Multiply the values in the X variable of the table letter by the aspect ratio of 1.5.Reassign the result back to X so that letter contains the corrected data

Answer 1

[Image Analyst]

You can discover why once you look at this link. You might also like to look at the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_fix_the_error_.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22.3F

[Mohamed Ahmed]

i know this way of indexing. What i mean in my question that

for this command

 testmat= matrix(idtest,:)

"idtest" is a logical type with 569 row of zeros, wasn't it supposed to return an empty array ?

i tried the same steps but by the following:

 idtest=logical(zeros(569,1))
testmat= matrix(idtest,:)

this gave me an o/p of empty matrix

but when using those commands

idtrain = training(c);

testmat= matrix(idtest,:)

the o/p of idtrain is 569 row and 1 column but the o/p of testmat is not an empty matrix

so, what's the difference?

[Walter Roberson]

Please show

class(idtest)
nnz(idtest)

[Mohamed Ahmed]

When trying :

 idtest=test(c);
    testmat= matrix(idtest,:);
The o/p is:
ans =
logical

ans =

     1

When trying:

idtest=logical(zeros(569,1));

testmat= matrix(idtest,:);

the o/p is:

logical

ans =

     0

[Walter Roberson]

The original idtest is not all zero. You can use

[row, column] = find(idtest)

to see the row and column of the one (and only one) non-zero entry in it.

[Mohamed Ahmed]

Thanks very much.