CODEWITHSUNDEEP
arraysmatlabtypes
makansij
makansij

Reputation: 9865

Matlab size function datatype output?

For some reason when I try the size function in matlab, I cannot determine the datatype and cannot use it the way I want.

data = [[3,4,56,1,2],[3,1,3,45,2]];

Then, I want to get the second dimension:

size(data)(2)

throws an error:

>> size(data)(2)
Error: ()-indexing must appear last in an index expression.

Then I try this:

>> n = size(data)

n =

     1    10

>> n(2)

ans =

    10

And it is no problem. Blows my mind. why? and, what type of data type does size return?

Upvotes: 1

Views: 127

Answers (2)

Narendran Muraleedharan
Narendran Muraleedharan

Reputation: 78

That is not allowed in MATLAB, as your error says. To use the size function on a multi-dimensional array (matrix), use size(data, 1) to get the number of rows and size(data, 2) to get the number of columns.

Here is the (first bit of the) result from help size on MATLAB.

>>help size
'size' is a built-in function from the file libinterp/corefcn/data.cc

 -- Built-in Function: size (A)
 -- Built-in Function: size (A, DIM)

 Return the number of rows and columns of A.

 With one input argument and one output argument, the result is
 returned in a row vector.  If there are multiple output arguments,
 the number of rows is assigned to the first, and the number of
 columns to the second, etc.

Similarly, if you have a matrix A = [1, 2, 3; 4, 5, 6], use the same method to access the elements. For example, A(1,1) = 1 (NOT A(1)(1)), and A(2,2) = 5.

Cheers!

EDIT: Also, did you mean data = [[3,4,56,1,2];[3,1,3,45,2]]; (notice the semi-color separating the rows)? Because data = [[3,4,56,1,2],[3,1,3,45,2]]; would return a long 10-dimensional vector instead of a 5x2 matrix.

Upvotes: 1

DarthSpeedious
DarthSpeedious

Reputation: 1007

Try size(data,2). This is pretty basic.

Upvotes: 2

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