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# 8.3. Using a Single Spreadsheet Function for Linear Curve Fitting

## Problem

You want to perform a quick linear curve fit without using chart trendlines and without having to write the least-squares formulas yourself.

## Solution

Use Excel's `LINEST` function.

## Discussion

`LINEST` computes statistics for a least-squares straight line through a given set of data. The syntax for `LINEST` is `{= LINEST(` `y-value cell range` `,` `x-value cell range` `,` `compute intercept` `,` `compute statistics` `)}`. Note the braces surrounding this formula since it is an array formula. When you type this formula into a cell, you have to press Ctrl-Shift-Enter to enter it. Further, you have to select a 2 × 5 grid of cells before typing and entering the formula. This is because `LINEST` returns an array of data containing the various statistics computed for the best-fit line.

The first argument in `LINEST` is a cell range containing the y-values for the data to be fit, and the second argument is a cell range containing the x-values. The third argument is a logical value (`true` or `false`) specifying whether or not to force the intercept of the fit line to pass through zero. If `true`, the intercept is calculated in the usual least-squares manner. If `false`, the intercept is forced to zero, with the slope computed accordingly. The fourth argument is a logical value indicating whether or not to display extended statistics for the best-fit line. These extended statistics include such things as standard errors and residual sums. (See the "LINEST" ...

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