% randi() generates uniformly distributed pseudorandom integersįrom the example above, it is clear that we can use end reserved keyword for both rows and columns. We are interested to return the odd elements of rows and even elements of columns: Let’s assume that we have a 4-by-8 matrix with random numbers. However, in the case of subscript indexing, we need to specify the indices for both rows and columns. We can use what we learned in the first lesson about vectors to index a matrix/array. Nonconsecutive elements multiple elements indexing using another vector = ind2sub(size(sampleMatrix1), )įor the rest of this course, we use pair (row,col) subscript indexing unless otherwise mentioned. Sub2ind(size(sampleMatrix1), , )Īlternatively, we can use ind2sub command to find the associated row-column subscripts from a given set of linear indices: % Matrix size, row indices, column indices This single column is composed of all of the columns from the matrix, each appended to the last as shown in the figure below: In fact, MATLAB stores matrices and arrays not in the shape that they appear when displayed in Command Window as in the figure above, but as a single column of elements. We can also refer to the elements of a matrix with a single subscript instead of a pair of (row,col) number, i.e., arrayName(k) where arrayName is the name of the array in your code. It can be seen that every element has a unique pair of (row,col) number that can be used for indexing. For instance, if we want to retrieve the element in row 2 and column 3, we can say arrayName(2,3), where arrayName is the name of the array in your code. In this approach, the indices of the rows and columns can be specified for indexing. Both ways are explained in the following sections. There are two ways for indexing an array/matrix in MATLAB, which are subscript and linear indexing. To return the number of rows and columns of a matrix, we can use:Īlternatively, you can obtain the number of rows and columns with a single command: We can use magic(n) function, which returns an -by- matrix constructed from the integers 1 to. An -by- 2D array can be illustrated as follows: Let’s start with 2D arrays or matrices in MATLAB. That’s the reason for different operations for matrix and array in MATLAB, as discussed in here. Early versions of MATLAB supported only 2D matrices, not n-dimensional arrays. Note that the word “matrix” typically refers to a 2D array, whereas an “array” can be n-dimensional.
Arrays in MATLAB can be 2 or 3 dimensional or even higher.
Matrix definitionĮvery variable in MATLAB is an array that can hold many numbers, characters, strings, date and times, and so on. This is part 2 in which “Matrices and Indexing” are explained. “MATLAB Vectorization Demystified”: In this series, I try to explain vectorization operation in MATLAB in details step-by-step through several examples.