plotting Graph in 3D help (2024)

thank you @Umar for your response but i dont understand how to use plot3 command for this particular code. As i have values for x and y but for z what values are to be used?

Hi Fareeha,

To modify the code for 3D plotting using plot3, you would need to have additional data representing a third dimension. For instance, if you have a third variable z that corresponds to the velocity values, you can modify the plotting section as follows.

% Assuming z represents the third dimension data z = sin(x); % Example third dimension data

figure(2) plot3(x, y(2, :), z, 'linewidth', 1.5); xlabel('\eta', 'fontweight', 'bold', 'fontsize', 16) ylabel('f^{\prime}(\eta)', 'fontweight', 'bold', 'fontsize', 16) zlabel('z-axis Label', 'fontweight', 'bold', 'fontsize', 16)

In this modified code snippet, plot3 is used to create a 3D plot with x, y(2, :), and z representing the three dimensions. You can adjust the z values based on your specific data.Remember, when transitioning from 2D to 3D plotting, ensure that your data is appropriately structured to represent the third dimension accurately for meaningful visualization using plot3.

@Umar what if i don;t know what is z, then? can you help me understanding with an example using same code?

@Umar does contour command work for this?

Hi Fareeha,

To answer your question about z in your example code, it will be set to zeros to plot the data in 3D space.

Also, in the provided function basic, which involves solving a boundary value problem using bvp4c, the primary focus seems to be on plotting the velocity profile rather than generating contour plots.

Here is a full version of your code by graphing plot in 3D.

In the updated code snippet, the plot3 function is used to create a 3D plot of the velocity by enhanceing visualization by adding a third dimension to the plot. In this case, the velocity data is plotted in 3D space, providing a more comprehensive view of the results. Additionally, a Z-axis label is added to the plot for clarity. The rest of the code remains the same, defining parameters, handling boundary conditions, and solving the system of first-order ODEs as before. Your bc2D function still calculates the residual of the boundary conditions, while the bvp2D function defines the system of ODEs to be solved using the bvp4c solver.

Hope this will help resolve your problem.

Thankyou @Umar I also want to generate contour plot. how can i adjust these values to generate contour?

@Umar i also want to use a loop for generating graph for different values of parameters. like i want to variate K from 1 to 3 for fixed values of n and lam, can you help me doing this?

Hi Fareeha,

To modify the existing code for generating a contour plot, we need to adjust the plotting section and include the necessary commands to create a contour plot. Below is the updated code with modifications for generating a contour plot:

function basic

K = 0.2; n = 0.3; lam = 0.1;

% Defining parameters

sol1 = bvpinit(linspace(0, 6, 300), [0 0 0 0 0]); sol = bvp4c(@bvp2D, @bc2D, sol1); x = sol.x; y = sol.y;

% Plotting the velocity in 3D figure(1)

% Plotting in 3D plot3(x, y(2, :), zeros(size(x)), 'linewidth', 1.5); hold on

xlabel('\eta', 'fontweight', 'bold', 'fontsize', 16) ylabel('f^{\prime}(\eta)', 'fontweight', 'bold', 'fontsize', 16) zlabel('Z-axis Label') % Adding Z-axis label

% Generating Contour Plot

figure(2) contourf(x, y(2, :), 'LineWidth', 1.5); % Creating a filled contour plot colorbar; % Adding a color bar for reference xlabel('\eta', 'fontweight', 'bold', 'fontsize', 16) ylabel('f^{\prime}(\eta)', 'fontweight', 'bold', 'fontsize', 16) title('Contour Plot') % Adding a title to the plot

% Residual of the boundary conditions function residual = bc2D(y0, yinf) residual = [y0(1); y0(2) - 1; y0(4) + n * y0(3); yinf(2) - lam; yinf(4)]; end

% System of First Order ODEs function yvector = bvp2D(~, y) yy1 = (1 / (1 + K)) * (-y(1) * y(3) + y(2)^2 - K * y(5) - lam^2); yy2 = (2 / (2 + K)) * (-y(1) * y(5) + y(2) * y(4) + K * (2 * y(4) + y(3))); yvector = [y(2); y(3); yy1; y(5); yy2]; end

end

In this updated code, a new figure (Figure 2) is created to display the contour plot using the contourf function. The contourf function generates a filled contour plot based on the values of x and y(2, :). Additionally, a color bar is added to provide a reference for the contour levels.

By incorporating these modifications, the code will now produce a contour plot alongside the existing 3D plot, offering a visual representation of the data in a different format.

@Umar thank you, I executed this code and found this error:

Error using contourf (line 57)

Z must be at least a 2x2 matrix.

Error in basic(line 10)

contourf(x, y(2, :), 'LineWidth', 1.5);

@Umar thank you, i have just used z=peak(); in my code and able to generate contour.. I am attaching figure for reference.. can you tell how to check whether i am getting right figure?

can i use Z=peak(); in my code?