Update value of one variable from another variable in shiny

Question

How to update the value of one variable from another variable in shiny?

My dataset consists of sales and profit of various products, which I'm trying to show average and SD and perform more visualization using the value.

What i need - when the inputs are given if no data exists that matches the condition, then the variable should take default value and update the other variable. I select year and goal of sales, if no products reach a goal that year, then update the sales value to average value