MATLAB help. I have the function file written, but how do I do the main method file?

Write a user-defined function called geometric_plot() that takes numeric single-element arrays N, a, and r as input arguments and that plots the first N terms of the following geometric series on an appropriately constructed stem plot where the independent variable of the plot is k and the dependent variable of the plot is the kth term in the series: ark k=0 Note that a is the first term of the series and r is the common ratio. Check that the user's input value for N is an integer value greater than or equal to 1; if it is not have the user enter a new value. Write a script file called "YourName_Lab5_Task3.m that illustrates how this function works. Don't forget to include explanatory text for any results