Calculate Imbalance Ratio for a multi-class dataset
IR = (negative_class/positive_class)
Where positive_class is the number of minority class samples and negative_class is the number of majority class samples.
How can i calculate Imbalance Ratio for a dataset which is imbalanced? I came across a way in which it defined (it's taken from a paper):

given by the imbalance ratio (IR), defined as the ratio of the number of instances in the majority class to the number of examples in the minority class

Now, is this one of the right ways to calculate?
Thanks