In a continuation from the previous tip, we look at some basic built-in functions for determining trendline coefficients of a X-Y plot.

For a series of X-Y values that we suspect have a linear relationship, we can determine the slope and y-intercept values of the linear approximation using the builtin functions **SLOPE()** and **INTERCEPT** as showb below. Compare these values to those we obtained when performig our regression analysis without using the builtin functions.

Now, plotting X-Y data is straightforward. Adding a trendline takes a little more work. We start off with the basic X-Y plot.

First, select the chart for editing by right-clicking anywhere inside the chart boundary. Now, before we add the trendline, we need to select the data series for editing. Move the cursor over one of the data points – you will see popup info about the nearest data point.

Left-click and the data series is now selected (below)

The **Data Series** dialog opens up. Select the **Statistics** tab (below). Select the Linear Regression curve and click **OK**

The modified X-Y plot with the newly added trend line.