![]() The rand() function creates an array of uniformly distributed random numbers on (0,1). The zeros() function creates an array of all zeros. The eye() function creates an identity matrix. The ones() function creates an array of all ones. We have a lot of functions that create arrays. Here 3 is the row number and 1 is the column numberĪnother way of doing it is specifying the product of column index and row index The most common way is to specify the row and column subscripts, such as There are two ways to refer to a particular element in an array. The first element has 2 positions ie column index number and rows index number.Ī = ![]() Indexing is the process of selecting an element in an array based on its position in the array. When you want to access selected elements of an array, use indexing. In MATLAB®, every variable is an array that can hold many numbers. Instead, they are performed between two entire matrices. "Matrix operations," on the other hand, are not implemented on corresponding elements in the two arrays. In other words, they are element-by-element operations. "Array operations" are implemented on corresponding elements in the two arrays. In MATLAB, two categories of operations are available between arrays: array operations and matrix operations. The 'a' variable is stored in the workspace, and the terminal will display the output in the command window asĪ = 1 2 3 4 5 6 7 8 9 10 11 12 Array Operations in MATLAB ![]() It creates an array variable 'a' having one row and four columns. The second way is to use commas in between elements: The 'A' variable is stored in the workspace, and the terminal will display the output in the command window as: It creates an array variable 'A' with one row and four columns. The first way is to use spaces between elements: Note that in the latter two cases is a one-dimensional vector, and should be reshaped back into a matrix if necessary (for example, using reshape).In MATLAB, we can create arrays in multiple ways. For instance, if we have: A = Īnd we want to extract A(, ) using logical indexing, we can do either this: Ir = logical() The subscript vector must be either of the same dimensions as the original matrix or a vector with the same number of elements. In logical indexing the subscripts are binary, where a logical 1 indicates that the corresponding element is selected, and 0 means it is not. For example, if you want to convert the subscripts in matrix A (corresponding to element 30) into a linear index, you can write sub2ind(size(A), 1, 3) (the result in this case should be 7, of course). The resulting matrix is, however always of the same dimensions as the subscript matrix.įor instance, if I =, then A(I) is the same as writing reshape(A(I(:)), size(I)).Ĭonverting from matrix subscripts to linear indices and vice versa:įor that you have sub2ind and ind2sub, respectively. The subscript matrix is simply converted into a column vector, and used for linear indexing. It is also possible to use another matrix for linear indexing. For that reason, A(:) converts any matrix A into a column vector. The special colon and end subscripts are also allowed, of course. The equivalent column vector is: A = [10 For instance, we have: A = Īnd we want to compute b = A(2). Linear indexing treats any matrix as if it were a column vector by concatenating the columns into one column vector and assigning indices to the elements respectively. This is especially useful for large matrices. ![]() The colon is just a short-hand notation for "1:end".įor example, instead of writing A(, ), you can write A(:, 2:end).end simply indicates the last index in that dimension.There are also two special subscripts: end and the colon ( :): %# Extract the first and third rows, and the first and second columnsī = A(, ) %# B = Indexing vectors can be specified for each dimension separately, for instance: A = %# Extracts the third and the ninth element They can either contain a single index or several, like so: A = Indexing vectors indicate the indices of the element to be extracted. There's an interesting article in the official documentation that comprehensively explains indexing in MATLAB.īasically, there are several ways to extract a subset of values, I'll summarize them for you: 1. The simplest way to extract the desired sub-matrix would be with an index vector: B = A(, ) As for your question, suppose you have an arbitrary 10-by-10 matrix A.
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