Excel - Microsoft Excel TREND Function

Description

The Excel TREND function calculates the trend line through a given set of y-values and (optionally), a given set of x-values. The function then extends the linear trendline to calculate additional y-values for a further supplied set of new x-values. 

The syntax of the function is : 

TREND( known_y's, [known_x's], [new_x's], [const] ) 

Where the arguments are as follows : 

If more than one new y-value is to be calculated by the Excel Trend function, the new values will be returned as an array. Therefore, the function must be entered as an Array Formula. 

Array Formulas: 

To input an array formula, you need to first highlight the range of cells for the function result. Type your function into the first cell of the range, and press CTRL-SHIFT-Enter.

Go to the Excel Array Formulas page for more details. 

Trend Function Example

The spreadsheet below shows a simple example of the Excel Trend Function being used to extend a series of x- and y-values that lie on the straight line y = 2x + 10. These are stored in cells A2 - B5 and are also shown in the graph. 

The Trend function uses the least squares method to find the straight line that has the best fit for the provided known x- and y- values. In this simple example, the line of best fit is the straight line y = 2x + 10. 

Once Excel has calculated the straight line equation, it can use this to calculate the new y-values for the provided new x values. 

In this example, the values of the [new_x's] are stored in cells A8 - A10 and the Excel Trend function has been used, in cells B8 - B10, to find the corresponding new y values. The equation for this, as shown in the formula bar, is : 

=TREND( B2:B5, A2:A5, A8:A10 ) 

It is seen that the Trend function in the formula bar is encased in curly braces { }. This indicates that the function has been input as an Array Formula. 

Note that, although the points in the example fit exactly along the straight line y = 2x + 10, this is not essential. The Excel Trend function will find the line of best fit for any set of values provided to it. 

Trend Function Errors

The most common errors from the Excel Trend function are listed in the table below : 

Common Errors