# TREND function

This article describes the formula syntax and usage of the **TREND** function (function: A prewritten formula that takes a value or values, performs an operation, and returns a value or values. Use functions to simplify and shorten formulas on a worksheet, especially those that perform lengthy or complex calculations.) in Microsoft Excel.

## Description

Returns values along a linear trend. Fits a straight line (using the method of least squares) to the arrays known_y's and known_x's. Returns the y-values along that line for the array of new_x's that you specify.

## Syntax

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

The TREND function syntax has the following arguments (argument: A value that provides information to an action, an event, a method, a property, a function, or a procedure.):

**Known_y's**Required. The set of y-values you already know in the relationship y = mx + b.- If the array known_y's is in a single column, then each column of known_x's is interpreted as a separate variable.
- If the array known_y's is in a single row, then each row of known_x's is interpreted as a separate variable.
**Known_x's**Required. An optional set of x-values that you may already know in the relationship y = mx + b.- The array known_x's can include one or more sets of variables. If only one variable is used, known_y's and known_x's can be ranges of any shape, as long as they have equal dimensions. If more than one variable is used, known_y's must be a vector (that is, a range with a height of one row or a width of one column).
- If known_x's is omitted, it is assumed to be the array {1,2,3,...} that is the same size as known_y's.
**New_x's**Required. New x-values for which you want TREND to return corresponding y-values.- New_x's must include a column (or row) for each independent variable, just as known_x's does. So, if known_y's is in a single column, known_x's and new_x's must have the same number of columns. If known_y's is in a single row, known_x's and new_x's must have the same number of rows.
- If you omit new_x's, it is assumed to be the same as known_x's.
- If you omit both known_x's and new_x's, they are assumed to be the array {1,2,3,...} that is the same size as known_y's.
**Const**Optional. A logical value specifying whether to force the constant b to equal 0.- If const is TRUE or omitted, b is calculated normally.
- If const is FALSE, b is set equal to 0 (zero), and the m-values are adjusted so that y = mx.

## Remarks

- For information about how Microsoft Excel fits a line to data, see LINEST.
- You can use TREND for polynomial curve fitting by regressing against the same variable raised to different powers. For example, suppose column A contains y-values and column B contains x-values. You can enter x^2 in column C, x^3 in column D, and so on, and then regress columns B through D against column A.
- Formulas that return arrays must be entered as array formulas.

** Note ** In Excel Online you cannot create array formulas.

- When entering an array constant for an argument such as known_x's, use commas to separate values in the same row and semicolons to separate rows.

## Example

The workbook below shows examples of this function. Inspect them, change existing formulas, or enter your own formulas to learn how the function works.

To work more in-depth with the example data in Excel, download the embedded workbook to your computer, and then open it in Excel.