You can use the Regression tool instead of the LINEST worksheet function. Note The Regression tool alerts you to this problem and does not continue. Do not overlap the x- and y-value ranges when referencing cells in the formula. Normal statistical probability disallows the values in the x and y ranges to overlap (duplicate each other). If the x-value and y-value ranges overlap, the LINEST worksheet function produces incorrect values in all result cells. Workaround Case 1: The x-value and y-value ranges overlap You specify a zero constant (set the third argument of the LINEST function to True). The number of rows in the input range is less than the number of columns in the total range (x-value plus y-value). The range of x-values overlaps the range of y-values. The output returned from LINEST may be incorrect if one or more of the following conditions are true: The Regression tool in the Analysis ToolPak may also return incorrect values. When you use the LINEST worksheet function in a worksheet in Microsoft Excel, the statistical output may return incorrect values. Incorrect output is returned when you use the Linear Regression (LINEST) function in Excel Symptoms
