Plotting data in MATLAB is a fundamental skill that every researcher, engineer, or scientist needs to master. MATLAB provides powerful tools and functions for creating a wide range of plots, from simple 2D plots to complex 3D visualizations. One common requirement in data visualization is the need to plot multiple data sets with different scales on the same graph.
Plotting with two axes in MATLAB can be really useful when you want to compare two different variables that have different units or ranges of values. For example, you may want to plot temperature and humidity data on the same graph, but temperature values can range from -20°C to 40°C, while humidity percentages range from 0% to 100%. Using two axes allows you to effectively visualize both variables without losing any information.
In MATLAB, you can create a plot with two axes using the yyaxis function. This function allows you to specify the axes where the data will be plotted, and you can choose between left (‘left’) or right (‘right’) axes. Once you have created the axes, you can use the plot function to plot your data as usual. MATLAB will automatically adjust the scales and plot the data correctly on the two axes.
In addition to using two axes, you can further enhance your plots by adding labels, titles, legends, and customizing the appearance of the lines and markers. By combining all these features, you can create professional-looking plots that effectively communicate your data to others.
In this article, we will walk you through the step-by-step process of plotting data with two axes in MATLAB. We will provide code examples and explain the different options and functions available to customize your plots. Whether you are a beginner or an experienced MATLAB user, this article will help you master the art of plotting with two axes and improve your data visualization skills.
Step-by-Step Guide
To plot data with two axes in MATLAB, you can follow these step-by-step instructions:
Step 1: Open MATLAB and create two vectors with the same length, representing the x-axis and the y-axis data.
Step 2: Define the first plot using the plot() function, specifying the x-axis and y-axis data as arguments.
Step 3: After the first plot, call the hold on command to enable the addition of multiple plots to the same axes.
Step 4: Define the second plot using the plot() function, specifying the x-axis and y-axis data as arguments. This plot will be superimposed on the first plot.
Step 5: Call the hold off command to disable the addition of multiple plots to the same axes.
Step 6: Use the xlabel() function to provide a label for the x-axis and the ylabel() function to provide a label for the y-axis.
Step 7: Use the axes() function to create a second set of axes with a different scale on the right side of the figure.
Step 8: Use the plot() function again to define a plot on the second set of axes, specifying the x-axis and y-axis data as arguments.
Step 9: Use the xlabel() function to provide a label for the x-axis of the second set of axes and the ylabel() function to provide a label for the y-axis of the second set of axes.
Step 10: Use the legend() function to add a legend to the plot, specifying the labels for each plot as arguments.
Step 11: Use the title() function to add a title to the plot.
By following these steps, you can easily plot data with two axes in MATLAB and customize the appearance of the plot according to your requirements.
Step 1: Creating the data
In order to plot with two axes in Matlab, you first need to create the data that you want to plot. This data can be generated using various methods, depending on the type of data and the desired representation.
For example, if you want to plot two sets of data on the same graph, each with its own y-axis, you can create two vectors of data points. Let’s say you have a vector x representing the x-values, and two vectors y1 and y2 representing the y-values for the two sets of data. You can create these vectors using the linspace or the colon operator.
Here is an example of how to create the data:
x = linspace(0, 10, 100); % Creating the x-values
y1 = sin(x); % Creating the y1-values
y2 = cos(x); % Creating the y2-valuesIn this example, we use the linspace function to create 100 equally spaced values between 0 and 10, which will be our x-values. We then use the sin and cos functions to create the y-values for the two sets of data.
Once you have created the data, you can proceed to the next step, which is plotting the data.
Step 2: Plotting the first axis
Once you have your data ready, you can start plotting the first axis of your graph using MATLAB.
To plot the first axis, you can use the plot function in MATLAB. This function takes the data points for the x-axis and y-axis as its arguments.
Here’s an example of how to use the plot function:
x = [1, 2, 3, 4, 5]; % x-axis data points
y1 = [10, 20, 15, 25, 30]; % y-axis data points for the first axis
plot(x, y1);This code will create a line plot with the data points you provided. The x-axis will have values 1, 2, 3, 4, and 5, while the y-axis will have values 10, 20, 15, 25, and 30.
If you want to customize the appearance of the first axis, you can use various options provided by the plot function. For example, you can add a title to the axis, change the color of the line, or add markers to the data points.
Here’s an example that demonstrates some of these options:
x = [1, 2, 3, 4, 5]; % x-axis data points
y1 = [10, 20, 15, 25, 30]; % y-axis data points for the first axis
plot(x, y1, 'r-o'); % red line with circle markers
title('First Axis'); % title for the first axis
xlabel('X-axis'); % label for the x-axis
ylabel('Y-axis'); % label for the first axisThis code will create a line plot with a red line and circle markers. It will also add a title to the first axis and labels to the x-axis and the first axis.
By following these steps, you can plot the first axis of your graph in MATLAB. In the next step, we will look at how to plot the second axis.
Step 3: Plotting the second axis
To plot the second axis on your MATLAB plot, you can use the yyaxis function. This function allows you to create a plot with two y-axes, each with its own set of data.
Here is an example of how you can use the yyaxis function to plot two sets of data on the same plot with different y-axes:
x = 1:10;
y1 = x.^2;
y2 = 10*x;
figure;
yyaxis left;
plot(x, y1, 'r');
ylabel('y1');
yyaxis right;
plot(x, y2, 'b');
ylabel('y2');
xlabel('x');
legend('y1', 'y2');
In this example, we first define the x-values for our data points. Then, we create two sets of y-values: y1 and y2, which are calculated based on the x-values.
Next, we create a new figure and call the yyaxis function to set the left y-axis as the active axis. We then use the plot function to plot y1 against x with a red line.
We use the ylabel function to label the left y-axis as y1.
Next, we call the yyaxis function again to set the right y-axis as the active axis. We then use the plot function to plot y2 against x with a blue line.
We use the ylabel function again to label the right y-axis as y2.
Finally, we use the xlabel function to label the x-axis as x. We also add a legend to the plot to distinguish between the two lines.
You can customize the appearance of your plot by using additional functions and properties, such as title, grid, and linewidth. Experiment with different settings to achieve the desired look for your plot.
By following these steps, you can easily plot data with two y-axes in MATLAB and create informative and visually appealing plots.
Step 4: Formatting the axes
After creating the plot with two axes, you may want to format the axes to make them more readable and visually appealing. Here are some options for formatting the axes in MATLAB:
Changing the labels
To change the labels of the x-axis or the y-axis, you can use the xlabel and ylabel functions. For example, if you want to change the label of the x-axis to “Time” and the label of the y-axis to “Temperature”, you can use the following code:
xlabel('Time');
ylabel('Temperature');Setting the axis limits
To set the limits of the x-axis or the y-axis, you can use the xlim and ylim functions. For example, if you want to set the limits of the x-axis to range from 0 to 10 and the limits of the y-axis to range from -5 to 5, you can use the following code:
xlim([0 10]);
ylim([-5 5]);Changing the tick marks
To change the tick marks on the x-axis or the y-axis, you can use the xticks and yticks functions. For example, if you want to set the tick marks on the x-axis to be at 0, 2, 4, 6, 8, and 10, you can use the following code:
xticks([0 2 4 6 8 10]);Adding grid lines
To add grid lines to the plot, you can use the grid function. For example, if you want to add grid lines to both the x-axis and the y-axis, you can use the following code:
grid on;These are just some examples of how you can format the axes in MATLAB. Depending on your specific needs, you may want to explore other options available in the MATLAB documentation.
Step 5: Adding labels and titles
After creating the plot with two axes, it is important to add labels and titles to enhance the overall presentation. These elements provide information and context to the plot, making it easier for the audience to understand the data being represented.
Adding a title
To add a title to the plot, you can use the title function in MATLAB.
For example, if you want to add the title “Temperature and Humidity Data” to the plot, you can use the following code:
title('Temperature and Humidity Data');This will create a title at the top of the plot, centered horizontally.
Adding labels to the axes
To add labels to the x-axis and y-axis, you can use the xlabel and ylabel functions in MATLAB, respectively.
For example, if you want to label the x-axis as “Time (hours)” and the y-axis as “Temperature (°C)”, you can use the following code:
xlabel('Time (hours)');
ylabel('Temperature (°C)');This will create labels next to the respective axes, providing information about the data being represented.
By adding labels and titles to your plot, you can make it more informative and visually appealing, helping your audience to better understand the data being presented.
