how to make a function that discreminate between scalar and vectors in matlab

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Muhammad Usman Saleem 2015-5-20

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评论： Star Strider 2015-5-20

Hi; I am going to make a function that classify inputs.If the input is a vector it generate 0 and if it is empty scalar matrix it gives -1 and for matrix it gives 1 I am using that codes

function myclass=classify(x)
if size(x)==0 0
    myclass=-1;
elseif size(x)~=0 0 
    myclass=1;
end
end
This codes run perfectly for empty matrix and matrix but i getting in troble how i can define it to discriminate for vector(having 1 row or col). I hope i have to use two more ifs in elseif one will check for vector and other for matrix. I stuck how it implement .Kindly guide me about correction..Thanks in advacne

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Muhammad Usman Saleem 2015-5-20

This codes run perfectly for empty matrix and matrix but i getting in troble how i can define it to discriminate for vector(having 1 row or col). I hope i have to use two more ifs in elseif one will check for vector and other for matrix. I stuck how it implement .Kindly guide me about correction..Thanks in advacne

Stephen23 2015-5-20

编辑：Stephen23 2015-5-20

What exactly is an "empty scalar matrix"? By definition a scalar is a 1x1 array, and thus cannot be empty. This is clearly documented here:

http://www.mathworks.com/help/matlab/math/empty-matrices-scalars-and-vectors.html

In any case, what is wrong with the inbuilt functions: isempty, isscalar, isvector, ismatrix, isrow, iscolumn... ? Did they stop working?

Maybe reading this would help:

http://www.mathworks.com/help/matlab/basic-information.html

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Star Strider 2015-5-20

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在 MATLAB Online 中打开

You need to use the any and all functions in your comparisons:

function myclass=classify(x)
myclass = 0;
if any(size(x)==0)
    myclass=-1;
elseif all(size(x)>1)
    myclass=1;
end
end

This worked for me.

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Muhammad Usman Saleem 2015-5-20

tell me where is the problem with my code.Kindly read the question mentioned above to better understand the problem..Thanks in advance

Star Strider 2015-5-20

在 MATLAB Online 中打开

If it’s a scalar, all dimensions have to be equal to 1, so this statement has to test for that:

elseif all(size(x)>1)

See if substituting the ‘double equal sign’ == helps.

Also, your default condition needs to be set to be sure it returns the correct value as described in: ‘Finally, if x is none of these, it returns 2.’

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Thorsten 2015-5-20

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编辑：Thorsten 2015-5-20

You should use Matlab's functions for your task: isempty, isscalar, ismatrix. Further, classify is a function in the statistics toolbox; you may want to choose a different name.

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Muhammad Usman Saleem 2015-5-20

i do not want to use build in functions.For fun i use checks..

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Stephen23 2015-5-20

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编辑：Stephen23 2015-5-20

在 MATLAB Online 中打开

This would be much simpler code without the if commands, even as an anonymous function:

>> fun = @(x) all(size(x)>1)-isempty(x);
>> fun([])
ans =
    -1
>> fun([1,2,3])
ans =
     0
>> fun([1,2,3;4,5,6])
ans =
     1

To do the whole thing without "inbuilt functions" then just replace the isempty(x) with any(size(x)==0). I doubt that any solution fulfills this though:

http://www.mathworks.com/matlabcentral/answers/38787-what-can-be-programmed-without-any-built-in-functions