Machine learning program question

2016 8 2
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更新时间：2020 5 30
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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.

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CHANDRU G
CHANDRU G 2020-5-30
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

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Image Analyst
Image Analyst 2016-8-3

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Mohamed Ahmed
Mohamed Ahmed 2016-8-3
编辑：Mohamed Ahmed 2016-8-3
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?
Mohamed Ahmed
Mohamed Ahmed 2016-8-4
编辑：Mohamed Ahmed 2016-8-4
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
Walter Roberson 2016-8-4
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.

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