For a given series we can add a trend line which, by applying the selected mathematical function, approximates and shows the trend of data, which was discussed in one of the earlier posts. By displaying the value of R2 we can see how well we chose the function that approximates the data. How else can you improve the trend line appearance?
Charts are often expected to present the current state and projection of future events. Nobody reliably knows what will happen in the future, but by approximating past data, it is possible to identify trends. Trend, by definition, represents the general direction of development or change. Excel sets trends and displays them using the trend line by application of various mathematical functions.