How do I Calculate the row % change when there are missing values in a Matrix

Hi I am having trouble with calculating the % difference between rows when there are empty values. 

My Variables are as followed:

C$ is the values

Countries is the different contries names

DATA_MONTH represents the time. 

Here is a screenshot of the data table: 

I used the Matrix visual, put DATA_MONTH in Rows, Countris in Columns and C$ in Values. Notice that there are some missing values here and there, how do i calcuate the row % change from here ?