MATLAB Programming
MATLAB Programming MATLAB Programming
1 Data Structures Function islogical isnumeric isreal isstruct Description Determine if input is a logical array. Determine if input is a numeric array. Determine if input is an array of real numbers. Determine if input is a MATLAB structure array. Example Using isnumeric and isreal Pick out the real numeric elements from this vector: A = [5+7i 8/7 4.23 39j pi 9-2i]; for m = 1:numel(A) if isnumeric(A(m)) && isreal(A(m)) disp(A(m)) end end The values returned are 1.1429 4.2300 3.1416 Data Structures Used in the Matrix These functions test elements of a matrix for a specific data structure. Function isempty isscalar issparse isvector Description Determine if input has any dimension with size zero. Determine if input is a 1-by-1 matrix. Determine if input is a sparse matrix. Determine if input is a 1-by-n or n-by-1 matrix. 1-26
Resizing and Reshaping Matrices Resizing and Reshaping Matrices You can easily enlarge or shrink the size of a matrix, modify its shape, or rotate it about various axes. This section covers • “Expanding the Size of a Matrix” on page 1-27 • “Diminishing the Size of a Matrix” on page 1-31 • “Reshaping a Matrix” on page 1-32 • “Preallocating Memory” on page 1-34 Expanding the Size of a Matrix You can expand the size of any existing matrix as long as doing so does not give the resulting matrix an irregular shape. (See “Keeping Matrices Rectangular” on page 1-8). For example, you can vertically combine a 4-by-3 matrix and 7-by-3 matrix because all rows of the resulting matrix have the same number of columns (3). Twowaysofexpandingthesizeofanexistingmatrixare • Concatenating new elements onto the matrix • Storing to a location outside the bounds of the matrix Note If you intend to expand the size of a matrix repeatedly over time as it requires more room (usually done in a programming loop), it is advisable to preallocate space for the matrix when you initially create it. See “Preallocating Memory” on page 1-34. Concatenating Onto the Matrix Concatenation is most useful when you want to expand a matrix by adding newelementsorblocksthatarecompatible in size with the original matrix. This means that the size of all matrices being joined along a specific dimension must be equal along that dimension. See “Concatenating Matrices” on page 1-7. 1-27
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1 Data Structures<br />
Function<br />
islogical<br />
isnumeric<br />
isreal<br />
isstruct<br />
Description<br />
Determine if input is a logical array.<br />
Determine if input is a numeric array.<br />
Determine if input is an array of real numbers.<br />
Determine if input is a <strong>MATLAB</strong> structure array.<br />
Example Using isnumeric and isreal<br />
Pick out the real numeric elements from this vector:<br />
A = [5+7i 8/7 4.23 39j pi 9-2i];<br />
for m = 1:numel(A)<br />
if isnumeric(A(m)) && isreal(A(m))<br />
disp(A(m))<br />
end<br />
end<br />
The values returned are<br />
1.1429<br />
4.2300<br />
3.1416<br />
Data Structures Used in the Matrix<br />
These functions test elements of a matrix for a specific data structure.<br />
Function<br />
isempty<br />
isscalar<br />
issparse<br />
isvector<br />
Description<br />
Determine if input has any dimension with size zero.<br />
Determine if input is a 1-by-1 matrix.<br />
Determine if input is a sparse matrix.<br />
Determine if input is a 1-by-n or n-by-1 matrix.<br />
1-26
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