Matlab learning journey (1)

I. script files and M function 1.1 script files

A script file is a collection of command lines and consists of a series of MATLAB commands, built-in functions, and m files. The script file is created in the MATLAB compiler and saved as a. m file. It is executed in sequence. The variables generated during execution are stored in the current workspace.

Note: The script cannot return output variables. All created variables are stored in the workspace, but the script can provide graphical output, just like using the graphic output function plot.

Example:

Use the M file editor, type a command, and save it as magicrank. M.

Array = zeros (1, 32 ); For N = 3:32 Array (n) = rank (MAGIC (n )); End Array Bar (array) % bar chart output result

Run the M file. The result is 1-1.

Figure 1-1 function running result Diagram

1.2 m Functions

M functions are also called subprograms. They must be called by MATLAB and have certain universality.

1.2.1 M Function Structure

In terms of structure, the biggest difference between M functions and script files is the addition of a "function declaration line ".

M Function Format: function [return variable table] = function name (input variable List)
Description
Function body statement
Call format: output variable = function name (input variable)

(1) The function definition name should be the same as the file storage name. When an M file contains multiple M functions, the first function is the main function, and the M file name must be the main function name;

2) The name of the function file in MATLAB must start with a letter. It can be any combination of letters, underscores, and numbers, but cannot exceed 31 characters.

3) M function comments are represented by rows starting with %. Help function_name displays the comments after the first row.

 

Ii. Data Analysis 2.1 polynomials and their functions

In Matlab, a one-dimensional vector is used to represent the multi-direction formula. The polynomial coefficients are stored in the vector in descending order. For example, the specific representation of Polynomial p (x) is as follows:

The following is a vector composed of coefficients:

2.1.1 polynomial Root

MATLAB provides functions for solving the root of a polynomial

Example: Root of Polynomial

In the command window, enter:

> P = [3,-,]; > R = roots (P)

The output result is as follows:

R = 4.0283 + 2.8554i 4.0283-2.8554i -2.3616 + 2.8452i -2.3616-2.8452i

2.1.2 polynomial operation

Polynomial functions

Calculation relationship	Corresponding function commands
Multiplication	Conv (A, B)
Division	[Q, R] = deconv (A, B) Q is the quotient of Polynomial a divided by polynomial B, and the remainder is R
Polynomial Derivation	Polyder (P)
Polynomial points	Polyint (P, K) returns the point of the polynomial P, and the point constant is K.

2.2 rational Polynomials

In many applications, such as Fourier, Laplace, and Z transformations, there is a ratio of two polynomials. The expansion functions of polynomials in Matlab are as follows:

[R, P, K] = residue (B,)

B. A is the polynomial coefficient vector of the numerator and denominator respectively. R, P, and K are the retention, pole, and direct items respectively.

For example, partial fraction is expanded and the result is

Code:

> A = [1 5 6]; > B = [1]; > [R, S, K] = residue (B,)

Output result:

R = -1.0000 1.0000 S = -3.0000 -2.0000 K = []