What does ~ mean in an assignment when calling a function?

Given this line of code to call the function named gradientDescentMulti:

[~, J_history1] = gradientDescentMulti(X, y, theta, alpha, num_iters)

and the defininion of the function as: function [theta, J_history] = gradientDescent(X, y, theta, alpha, num_iters) ,

is the ~ in the assignment matrix just assuming the default assignment for the function?

Answer 1

[Bruno Luong]

[~, J] = ....

mean the first output is ignored by the caller (assigned to a garbage if you like). Even that syntax exists, I often use

[trash, J] = ...
clear trash