When working with Julia, it is common to encounter situations where you need to modify a plot that was created outside of a function. This can be a bit tricky, but there are several ways to solve this problem. In this article, we will explore three different approaches to tackle this issue.
Approach 1: Using Global Variables
One way to modify a plot outside of a function is by using global variables. You can create the plot outside of the function and then modify it within the function by accessing the global variable. Here’s an example:
using Plots
# Create the plot outside of the function
plot = plot([1, 2, 3], [4, 5, 6])
function modify_plot()
# Access the global variable and modify the plot
plot = plot([1, 2, 3], [7, 8, 9])
end
# Call the function to modify the plot
modify_plot()
# Show the modified plot
display(plot)
This approach works by creating a global variable called “plot” and then modifying it within the “modify_plot” function. However, using global variables is generally not recommended as it can lead to code that is difficult to understand and maintain.
Approach 2: Passing the Plot as an Argument
A cleaner approach is to pass the plot as an argument to the function that needs to modify it. This way, you can avoid using global variables and make your code more modular. Here’s an example:
using Plots
# Create the plot outside of the function
plot = plot([1, 2, 3], [4, 5, 6])
function modify_plot(plot)
# Modify the plot
plot = plot([1, 2, 3], [7, 8, 9])
end
# Call the function to modify the plot
plot = modify_plot(plot)
# Show the modified plot
display(plot)
In this approach, the “modify_plot” function takes the plot as an argument and returns the modified plot. This way, you can easily reuse the function with different plots without affecting the global state of your code.
Approach 3: Using a Mutable Object
Another option is to use a mutable object, such as a dictionary or a mutable struct, to store the plot. This allows you to modify the plot within a function without using global variables. Here’s an example using a dictionary:
using Plots
# Create the plot outside of the function
plot = plot([1, 2, 3], [4, 5, 6])
function modify_plot(plot_dict)
# Modify the plot
plot_dict["plot"] = plot([1, 2, 3], [7, 8, 9])
end
# Create a dictionary to store the plot
plot_dict = Dict("plot" => plot)
# Call the function to modify the plot
modify_plot(plot_dict)
# Show the modified plot
display(plot_dict["plot"])
In this approach, the plot is stored in a dictionary called “plot_dict”. The “modify_plot” function modifies the plot by updating the value associated with the key “plot” in the dictionary. This way, you can modify the plot without using global variables.
After exploring these three approaches, it is clear that the second approach, which involves passing the plot as an argument, is the best option. It avoids the use of global variables and makes the code more modular and reusable. Additionally, it is easier to understand and maintain compared to the other two approaches.
