I want to read a matrix data with C. The data source is a matrix with n rows and 3 columns

I'm interested in sending it over and taking a look.

There are two sides.

The BAI method can be achieved:

Transpose Matrix: du

zhi b = a';

General method: reshape() function.

An example of a DAO is shown below:

Note: reshape(a,m,n) represents the matrix A is transformed into a matrix with M rows answering n columns, which is usually used to change the shape of the matrix, for example, the following ** converts the original 1 row and 4 column matrix into 2 rows and 2 columns matrix:

1. Prepare a "multi-dimensional multivariate sample data" that needs to be used for multi-dimensional multivariate line charts. xlsx”excel**。

2. Then use the version xlsread to read the multi-dimensional multivariate sample data of the established weight, and save the data and variable names to the MATLAB numerical matrix and cell matrix respectively.

3. Then use the size function to calculate the size of the multi-dimensional multivariate sample data.

4. Next, make a multi-dimensional multivariate graph, use the plot function, take a group of data each time to draw a line chart and then keep it, and draw all the lines in turn in multiple cycles.

5. Next, change the name of the variable whose abscissa is a multi-dimensional multivariable array.

6. Continue to add abscissa and ordinate labels as well as a title and display grid to the line chart.

To be precise, transpose is. '

b=a.';You can turn the sequence around.

And just one'It is conjugate transpose.

b=a';At the same time as transposing the sequence, the imaginary part reverses the opposite number.

However, for a series of real numbers, transpose and conjugate transpose are equivalent.

You can use the transpose function, and the usage is as follows:

a=[1 2 3 4 5];

b=a'Note that quotation marks are single quotation marks in the English input state, which represent transpose operations.

The transpose is the single quotation mark b=a';

var rows = "d:\");

var peopleinfotemps = => char ;

The type of peopleinfotemps is string[ length is the number of rows and columns you have. You can read it first.

Under your own package.

Use this to try reading the file.

Multidimensional array output.

string[items=

new string

foreach(string item in items)foreach(string item1 in item) Here output item1

Try it with this.

It's easy to read, and as for two-dimensional matrices, you don't know what it is.

1. Open MATLAB and enter a=[1 2 3 4; 4 5 6 7;1 2 3 4] and press enter to create a matrix with 3 rows and 4 columns.

2. If we want to get the data in column 3 of row 2 of the matrix, enter a(2,3).

3. If you want to get the first and third columns of the matrix, enter a([1 3],3).

4. If you want to obtain the continuous data of a certain column of the matrix, you can use a(1:2,3) to obtain the 1st to 2nd data of the third column.

5. Use a(2:end,3) to get the 3rd column, the 2nd to the last data, and get the matrix data as needed.

For example, if you have a 5 5 matrix, and you want to take the 3*2 matrix on its lower right foot, you should use the command:

a=zeros(5,5)

b = a (3:5, 4:5)% take a (3-5 rows, 4-5 columns).

b is taken.

Take a part of a matrix in MATLAB (for example, format A(m,n) to extract the part of matrix A that meets the requirements of m,n):

1. To extract an element, m,n are numeric scalars, such as a(2,3) is the element of the second row and the third column.

2. Extract a certain row and a certain column.

a(:,n) extracts all elements of column n, such as a(:,3) extracts all elements of column 3;

a(m,:) extracts all elements in row m, e.g. a(3,:) extracts all elements in row 3;

3. Extract any part and recompose a new matrix, continuous or discontinuous, monotonous or not monotonous.

Numeric designation: a([1 2 3 4],[2 3]) returns data for 1 2 3 4 rows and 2 3 columns;

The step size is specified: a(1:2:end,:)a(2:2:end,:) extract the odd and even rows of matrix a, respectively;

a(end:-1:1,:)a(:,end:-1:1) returns a matrix in reverse row order and column reverse order, respectively.

The variable specifies: a(b(:,1),: where the first column of b contains the data, which rows of matrix a are taken.

4. Variable specification, assuming that a matrix x1 stores coordinates, use the coordinates of matrix x1 to access the corresponding element in the matrix labels left:

for i = 1:size(x1,1)

x = labels_left(x1(i,2),x1(i,1));Match the number of labels in the left figure for pair 1.

For example, the original matrix is a=[1, 2, 3;4 5 6；7 8 9；10 11 12], now to generate b=[1 2; 4 5;7 8], i.e., two columns and three rows of the original matrix are extracted

b = a(1:3, 1:2)

Even if the extracted columns and columns are not continuous or the order needs to be reversed, it can be written as a([1,3,6], 4,3,1,5]).

MATLAB Matrix.

Extraction of elements and submatrices.

% Extraction of matrix elements.

a=[1 2 3;4 5 6;7 8 9;10 11 12]

a =1 2 3

a(3,1)% extracts elements from row 3, column 1 of the A matrix.

ans = 7>>> extracting elements by element numbers (matrix element numbers correspond one-to-one to the order in which they are stored!). )

a(6)ans = 5>> matrix elements in matlab are stored in columns, first in column 1, then in column 2...

>> use the function find(c) to find the rows and columns of matrix elements that match the criteria.

The format [row,col]=find(c) of the % function find(c) is usually a logical expression; row returns the row number of the element that satisfies the condition, and col returns the column number of the element that satisfies the condition.

a=[12 34 26 17 21;61 50 89 12 8;25 62 91 23 47]%Find elements greater than or equal to 20 and less than or equal to 60 in a matrix.

a =12 34 26 17 21

[r,c]=find(a>=20&a<=60);

b=find(a>=20&a<=60);

disp('Row and column numbers of eligible matrix elements:'),[r,c]

Row and column numbers of eligible matrix elements:

In MATLAB, you can use the baisize function to get the number of rows or columns of a matrix.

size(a) returns a row vector whose element DAO contains the length of the corresponding dimension of version a. For example, if a is a 2 3 matrix, then size(a) returns the vector [2,3].

The details are as follows.

1. The first step is to enter "a=[1 2 3; 2 4 6]", press enter to create a matrix with 2 rows and 3 columns, as shown in the following figure:

2. In the second step, enter "[m,n]=size(a)", press the enter key, you can see the number of rows and columns of the A matrix, m is the number of rows, n is the number of columns, as shown in the following figure:

3. In the third step, if we only want to get the number of rows of the matrix, we can enter "size(a,1)" as shown in the following figure:

4. Step 4: If you only want to get the number of columns of the matrix, you can enter "size(a,2)", as shown in the following figure:

The following function in MATLAB can obtain the number of rows (number of columns) of the matrix1, [m,n]=size(a) The row value of matrix A is assigned to m, and the number of columns is assigned to version n

m=size(a) m is a matrix of 1 2, weighted by the number of rows and columns of a, respectively.

2. m=length(a) assigns the maximum value in the number of rows and columns of matrix a to m, which is equivalent to max(size(a)).

Other manipulation functions commonly used for matrices in MATLAB:

ndims(a) returns the number of dimensions of a.

nnz(a) returns the number of non-0 elements in a.

The function to get the number of rows or columns in the matrix is as follows:

1. NDIMS(a) returns the dimension of a.

2. size(a) returns the maximum number of elements in each dimension of a3, length(a) returns max(size(a))4, [m,n]=size(a) if a is a two-dimensional array, returns the number of rows and columns5, nnz(a) returns the number of non-0 elements in a.

For example: matrix a=[1,2,3; 2,3,4] The number of rows is size(a,1)=2, and the number of columns(a,2)=3

The function to get the number of rows or columns in the matrix is as follows:

1. NDIMS(a) returns the dimension of a.

2. size(a) returns the most specialized of each dimension of a.

The number of genera of large elements.

3. length(a) returns max(size(a))4, [m,n]=size(a) if a is a two-dimensional array, returns the number of rows and columns5, nnz(a) returns the number of non-0 elements in a.

For example: matrix a=[1,2,3; 2,3,4]

The number of rows is size(a,1)=2

Number of columns size(a,2)=3

Gets the number of matrix rows or raids.

The function for the number of columns is as follows: bai

1. NDIMS(a) returns the dimension of dua.

2. size(a) returns a each zhi

The maximum number of elements in a dimension. dao

3. length(a) returns max(size(a)).

4. [m,n]=size(a) If a is a two-dimensional array, return the number of rows and columns.

5. NNZ(A) returns the number of non-0 elements in A.

For example, the matrix a=[1,2,3; 2,3,4]

The number of rows is set to size(a,1)=2

Number of columns dusize(a,2)=3

or zhinrow,ncol]=size(a); The number of rows is nrow=2, and the number of columns is ncol=3.

If you only need nrow, you can do it

Write for [nrow, genus]=size(a), return nrow=2;Similarly, [ ,ncol]=size(a), returns ncol=3;

How to divide 1000 equally portions? 22988 1000=, the number of columns must be an integer.

The extraction steps are as follows:

1. First, open the MATLAB command line window and enter a= [1 2 3; 4 5 6; 7 8 9;6 4 7] Create an a-matrix as shown in the image below and move on to the next step.

3. Then, after completing the above steps, press the Enter key, you can see that columns 1 to 3 of row 1 and row 2 of the matrix have been extracted, as shown in the figure below, and then enter the next step.

5. Finally, press the Enter key, and you can see that the first to second columns of the second to third rows of the matrix have been extracted. Once the method is learned, you can extract the matrix as needed, as shown in the figure below. In this way, the problem is solved.

Let's start with your question, the first row in parentheses, the first row is the line, the following is the column.

Using a(m,n) can extract the part of the matrix a that meets the requirements of m and n, the simplest is that m and n are both scalars, that is, a number, for example, a(1,1) a(2,3) returns the elements of a matrix with 1 row and 1 column and the elements of 2 rows and 3 columns respectively.

m,n can also be vectors, for example.

a([1 2 ],2 3]) returns data for 1 2 rows 2 3 columns.

There are also wild tricks, eg.

a(1,:) is all the data that returns the first row of the A matrix, which is equivalent to a(1,1:end) or a(1,1:size(a,2)).

m,n vectors can also be discontinuous, not monotonic, or have repetitions, for example.

a(1:2:end,:)a(2:2:end,:) extract the odd and even rows of matrix a, respectively, to form the matrix.

a(end:-1:1,:)a(:,end:-1:1) returns a matrix in reverse row order and column reverse order, respectively.

Suppose you want to extract the data in column nth of matrix a, using a(:,n) will do.

If you want to extract the first 3 data in column 2, you can use a (1:3,2).