MATLAB graphics drawing-contour map

Contour map

Suppose we want to draw a function:

xthe value range is -5 to 5, ythe value range is -3 to 3, and the increment is 0.1:

>> [x,y] = meshgrid(-5:0.1:5,-3:0.1:3);

The meshgridcommand is used to generate the grid.
We can also specify the increment first, and then call the meshgridcommand to generate the grid, for example:

>> x = [-5:0.1:5];
>> y = [-3:0.1:3];
>> [X,Y] = meshgrid(x,y);

It's just that we treat lowercase x,yas an intermediate variable, and the final value is X，Y.
If the function we draw is:

then we enter the following command:

>> z = X.^2 + Y.^2;

Now we call the contourcommand:

>> contour(X,Y,z)

The resulting image:
We can also add more content to this image:

• label
• The width between contour lines
• Line width
• Linear
• Line color
• Do not need to fill in. The
  above attributes can be modified using setcommands. It
  should be noted that when we return the attributes of the current image, because it is a two-dimensional grid, there are two parameters, which we can express in the form of a matrix:

>> [C,h] = contour(X,Y,z)

There are two parameters:

• C
  The first parameter represents x,ythe matrix of coordinates, which is a two-dimensional array
  

• h
hRepresents some properties:
  
  Of course, we can also use other letters to replace the names of these two parameters, as long as they are placed in an array.
  We call the setcommand:

>> set(h,'showtext','on','textstep',get(h,'levelstep')*2)

This time, we added a label to the contour plot:

Let's draw another function:

>> [x,y] = meshgrid(-5:0.1:5,-3:0.1:3);
>> z = cos(x).*sin(y);
>> [C,h] = contour(x,y,z);
>> set(h,'showtext','on','textstep',get(h,'levelstep')*2)

We can also call contour3commands to draw contours into three dimensions. If we call contour3(z,n), then he will produce a ncontour line with a level:

>> contour3(z,10)

This time we draw another function xwith ythe same value range as:

>> [x,y] = meshgrid(-2:0.1:2)
>> z  = y.*exp(-x.^2-y.^2);
>> contour(x,y,z),xlabel('x'),ylabel('y')

When two independent variables are in the same range, you can put:
[x,y] = meshgrid(x)

Let's draw three-dimensional:
just input:

>> contour3(x,y,z)

You get: