MATLAB built-in Tutorial Study Notes 2

Define the plural. For example:

X = 3 + 4I

 

Defines a matrix, similar:

A = [1 2 3; 4 5 6; 7 8 9]

 

Use SHIFT + F1 to view available functions, or directly click the FX button, for example:

 

 

Use rand to obtain a random number (within 0-1)

For example

Rand (3, 3)

Generate a Random Number Matrix with three rows and three columns;

To generate a Random Number Matrix with equal columns, you can use the rand (n) function, similar:

Rand (5 );

A Random Number Matrix of 5x5 is generated;

 

Use size to get the variable size, for example:

T = [1 2 3 4 5];

Size (t );

The result is 1 5, which is a row of 5 columns;

 

If

T = [1 2 3; 4 5 6; 7 8 9];

Size (t );

The result is three rows and three columns;

 

Matrix transpose, similar:

A = [1 2 3; 4 5 6; 7 8 9];

B = ';

It is to add a single quotation mark after;

 

You can use * to perform matrix multiplication directly. However, you must comply with the rules before Multiplication can be performed;

Otherwise, an error occurs, similar:

A = [1 2 3; 4 5 6; 7 8 9]

B = [1 2; 3 4]

Then a * B will report the following error:"

??? Error Using ==> mtimes
Inner matrix dimensions must agree.

"

 

. Operation, similar

A. * B

It is to multiply the elements corresponding to a and B. Likewise, it can be used in the/(Division) method, but Division is divided into the left and right vertices because of the difference of "/" and;

Similar;

A = [1 2; 3 4]

B ='

C = A./B

Output:

C =

1.0000 0.6667
1.5000 1.0000

 

However, when a. \ B is used, the output is:

C =

1.0000 1.5000
0.6667 1.0000

 

Use inv (n) to obtain the inverse matrix of the matrix, similar

A = [1 2; 3 4]

Inv ()

The output is:

Ans =

-2.0000 1.0000
1.5000-0.5000

 

You can use the matrix or array name a (m, n) to obtain the value of n columns in the m column of the Matrix, similar

A = [1 2 3; 4 5 6; 7 8 9]

A (2, 3)

Output:

Ans = 6

 

The following similar syntax can be used to output a specific area of the matrix:

A (1:3, 2: end)

Output

Matrix Values from 1-3 rows and 2-end Columns

 

Use

A (, :) indicates that all values in rows 1-3 are output, which replaces all columns. Similarly, a (:, 2: End) Outputs all columns whose ends are 2;

 

You can assign values to the above expressions, because their side effect is not the output value but the value in the matrix;

Therefore

A (:, 2: End) = 0

And then output A as follows:

A =

1 0 0 0
4 0 0 0
7 0 0 0
3 0 0 0

 

Use surf to create a 3D colored surface map (a 3D surface map) (I don't know what it is)

According to Baidu zhishang's statement:

Y = [];

W = y' * Y;

Surf (w );

The image is shown as follows:

 

MATLAB built-in Tutorial Study Notes 2