how we find a particular number from the matrix in matlab????

A=[2 3 4;5 4 6;7 8 4] suppose we want to select '4' of 1st row of 3rd column,2nd row of 2nd column and 3rd row of 3rd column.how did we find this number?????

Answer 1

[Stephen23]

It is not clear what numbers you want: when you write that you want "this number", are you referring to the indices of the fours in that matrix, or the fours themselves, or perhaps some other numbers? If you don't tell us exactly what you want, or what you need to do with these numbers, then it is difficult for us to provide you with a clear answer.

It seems that you want the indices of the fours, in which case here are some possible ways to get indices of values in a matrix:

>> A=[2 3 4;5 4 6;7 8 4] % data matrix
A =
     2     3     4
     5     4     6
     7     8     4
>> [R,C] = find(A==4) % row and column indices
R =
     2
     1
     3
C =
     2
     3
     3
>> L = find(A==4) % linear indices
L =
     5
     7
     9
>> X = A==4 % logical indices
X =
     0     0     1
     0     1     0
     0     0     1

And of course you can use any of these to extract those value from the matrix:

>> A(X)
ans =
   4
   4
   4

You can read more about indexing in the documentation:

http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

http://www.mathworks.com/help/matlab/math/matrix-indexing.html

[prema13]

thank u so much for solve my problem

[prema13]

A=[11 5 6 3 10 8 7 4 2 9 1;6 3 11 7 8 5 1 2 4 9 10;10 8 11 6 7 3 9 5 4 1 2;7 1 2 5 9 8 4 10 11 3 6;11 10 1 7 3 2 4 9 8 5 6].suppose we want to find whether 3, & 6 then which operator we have to choose???

[Stephen23]

You don't really tell us how you want to use this, which actually decides what method you want to use. So without any further details of what you are trying to achieve, you could use logical indexing:

>> A=[11 5 6 3 10 8 7 4 2 9 1;6 3 11 7 8 5 1 2 4 9 10;10 8 11 6 7 3 9 5 4 1 2;7 1 2 5 9 8 4 10 11 3 6;11 10 1 7 3 2 4 9 8 5 6]
A =
    11     5     6     3    10     8     7     4     2     9     1
     6     3    11     7     8     5     1     2     4     9    10
    10     8    11     6     7     3     9     5     4     1     2
     7     1     2     5     9     8     4    10    11     3     6
    11    10     1     7     3     2     4     9     8     5     6
>> X = A==3 | A==6
X =
     0     0     1     1     0     0     0     0     0     0     0
     1     1     0     0     0     0     0     0     0     0     0
     0     0     0     1     0     1     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     1     1
     0     0     0     0     1     0     0     0     0     0     1
>> A(X)
ans =
     6
     3
     6
     3
     6
     3
     3
     3
     6
     6

Also note that on MATLAB Answers it is considered polite to Accept an answer that best resolves your question.

[prema13]

how we partitioning this matrix.suppose 3 & 6 training data set or other than testing data set??

[Stephen23]

Then you can use the logical indexing to select the training and test sets:

 trainSet = A(X);
 testSet  = A(~X);

[prema13]

thx a lot

[prema13]

how we find trainSet or testSet in form of row or column????

[Stephen23]

It is not clear what you mean by "how we find trainSet or testSet in form of row or column": do you want to select columns of data from the matrix, or split the matrix column-wise into test and training sets?