Work with arrays

An array is a well-organized, numbered set of homogeneous data, having one name.

Access to the separate array cells is carried out on an integer index, i.e. on the number of element in an array. Depending on the amount of indexes, defining position of element in an array, arrays are divided into one-dimensional (vector-row, vector-column), two-dimensional (matrices) and multidimensional.

MatLab presents all data as an array, even a number is a two-dimensional array with a dimension one on one.

Work with vectors

Vectors are the one-dimensional (linear) numerical sets of numbers, position of every element is set by a singular value - its number.

Task of vectors

>> a1=[3 4 9 2] it is a vector-row

>> a1=[3, 4, 9, 2] it is a vector-row

>> a1=[3; 4; 9; 2] it is a vector-column

Task 7.

Set two vector-rows s1 = (3, 4, 9, 2) and s2 = (5, 3, 3, 2), find their sum and natural logarithm from the sum.

Access to vector elements is carried out by the task of its index in brackets after a name. It is possible to address to the block of consistently located elements of a vector by means of ":".

For example:

>> w=[0.1 2.9 3.3 5.1 2.6 7.1 9.8];

>> w(4)

ans =

5.1000

>> w(2:6)=0;

>> w

w =

0.1000 0 0 0 0 0 9.8000

Array cells can be included in expressions. For example, for being middle geometrical for the first three array cells, it is possible to do following:

>> w=[0.1 2.9 3.3 5.1 2.6 7.1 9.8];

>> gm(1/3)

gm =

0.9855

Task of vectors by means of operation ":". Let it is required to form the one-dimensional array of numbers in a range from 3.7 to 8.947 with an increase 0.3. It is easily arrived at by means of operator "colon". It is possible to define by means of function length, how many elements got in a vector.

>> mas=3.7:0.3:8.947;

>> length(mas)

ans =

18

Application of data processing functions to the vectors

Function	Application	Note
prod	>> z=[3 2 1 4 6 -5]; >> p=prod(z) p = -720	Multiplying of vector elements
length	>> z=[3 2 1 4 6 -5]; >> p=length(z) p = 6	Determination of number of vector elements
sum	>> z=[3 2 1 4 6 -5]; >> p=sum(z) p = 11	Adding up of vector elements
abs	>> z=[3 2 1 4 6 -5]; >> p=abs(z) p = 3 2 1 4 6 5	Determination of the module of vector elements
min	>> z=[3 2 1 4 6 -5]; >> p=min(z) p = -5	Determination of minimum element of vector
max	>> z=[3 2 1 4 6 -5]; >> p=max(z) p = 6	Determination of maximal element of vector
sort	>> z=[3 2 1 4 6 -5]; >> p=sort(z) p = -5 1 2 3 4 6   >> z=[3 2 1 4 6 -5]; >> [p, ind]=sort(z) p = -5 1 2 3 4 6 ind = 6 3 2 1 4 5	Vector ordering on increase       The call sort with two target elements forms a file of indexes of elements coincidence of the ordered and initial files
mean	>> z=[3 2 1 4 6 -5]; >> p=mean(z) p = 1.8333	Calculation of mean arithmetic vector

It is independently possible to know about the functions of data processing, executing the command help datafun.

Task 8.

 Set a vector, consisting of elements (9.4, - 2.3, - 5.2, 7.1, 0.8, 1.3).

 Find arithmetical mean elements of vector, using the functions sum and length. Check up a result, using the function mean.

 Order a vector on increase, find minimum and maximal elements of vector and their indexes.