# Using the LOGEST function in Microsoft Excel

The Microsoft Excel LOGEST function is very useful when finding the formula y = b*m^x for a curve but the help information in Excel is a little difficult to understand. This description should make it a bit easier.

This function will only work in some versions of Microsoft Office if the appropriate Add-in has been installed. This can be verified by checking in the Excel toolbar:- Tools, Add-Ins, Analysis ToolPak.

Two columns of data are made containing the known X and Y coordinates of the curve. An example of this can be found at log-spreadsheet-01.xls.

To understand the use of the LOGEST function either copy the whole table(A1:A12,B1:B12) into a new spreadsheet or delete the results (C18:D18 in the results box) in the existing spreadsheet and re-calculate.

Highlight the two cells that are to contain the results and select the LOGEST function from the toolbar at Insert/Function/Statistical/LOGEST and hit OK. The LOGEST box will appear and the cursor will be in the Known_y's box. Select the Y column (B2:B12) with the mouse and the cell references will appear in the Known_y's box.

Left click the mouse in the Known_x's box and select the X column (A2:A12) DMM Reading ( Volts) column with the mouse and the cell references will appear in the Known_x's box.

Left click the mouse in the Const box and enter a 1 for the constant which will ensure that b in the formula y = b*m^x is used.

Left click the mouse in the Stats box and enter a 0 for the stats which will ensure that the regression statistics are not returned.

Hit OK and then the keyboard function key F2 to enable both selected cells.

Press the CTRL + SHIFT + ENTER keys all together and the final calculation will be made.

Note: If the regression statistics are required, then a block of cells two wide and five deep needs to be selected before the function is inserted and 1 entered into the Stats box of the function.

This information is provided by Chemandy Electronics in order to promote the FLEXI-BOX