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Unformatted text preview: Vectors A vector the primary way MATLAB stores homogenous data (data of one type for example, all numbers, all letters, etc) Creating a vector Direct entry A = [1 2 3 4 5] Range-specification (colon operator) A = 1:5 OR A = 1:1:5 (both the same) (When the 1 in the middle of 1:1:5 is omitted, the step between each number is understood to be one) B = 1:2:7 = [1 3 5 7] Using the function linspace A = linspace(1,5,5) = [1 2 3 4 5] First number is the first element in the vector, second number is the last element in the vector, third number is the total number of elements in the vector Accessing/Manipulating a vector Indexing the primary method of accessing/removing/changing elements inside of a vector Create vector A: A = [1 2 3 4 5] To access the third element of A and assign it to a variable called B, do the following: B = A(3) Now, B is equal to the number 3 (which is the third element of A) To change the third element of A to the number 8, do the following: A(3) = 8 Now, A = [1 2 8 4 5] What if we wanted to make the 8 th element of A the number 4? If A only has 5 elements, will we receive an error? No MATLAB will compensate, filling in zeros for elements 6 through 7: A(8) = 4 Now, A = [1 2 8 4 5 0 0 4] To remove an item from a vector, set the vector indexed at the element in question equal to empty brackets ( ): A(5) = (delete the fifth element of A) Now, A = [1 2 8 4 0 0 4] Notice how the length of A decreased by one when we deleted an element (kind of obvious, but this has important later) All of these indexing techniques apply to ranges as well as single numbers; for example, to make the 1 st five elements of A equal to 3: A(1:5) = 3 Now, A = [3 3 3 3 3 0 0 4] To delete the first five elements of A: A(1:5) = Now, A = [0 0 4] Concatenating Vectors To Concatenate two vectors means to create a new vector by using elements of the old vectors. For example, Create vector A: A = [1 2 3 4 5] Create vector B: B = [6 7 8 9 10] Now, create vector C where C vectors A and B concatenated together: C = [A, B] Now, C = [1 2 3 4 5 6 7 8 9 10] This technique can also be combined with indexing to make a new vector with only certain elements of the first two vectors. For example, To create a new vector C from vectors A and B that consists of the first three elements of A and the last three elements of B: C = [A(1:3), B(end-2:end)] Now, C = [1 2 3 8 9 10] Note: the end operator is simply is another way of indexing from the last element of a vector; we can also specify indices using mathematical operations such as + and -. So, end-2 would be read by MATLAB as the last element of B minus two more elements. Thus, if B has five elements, then end-2 would be 5-2, or the third element (which in this case is the number 8). So another way of reading B(end-2:end) would be...
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- Spring '08