Excel features yet another group of functions closely related to the lookup and reference functions. Called information functions , they let you retrieve information about the type of content found in any particular cell you want to examine. You can find the full list of information functions in the Information group in the Insert Function dialog box (Insert → Function).
The most important information functions are those that start with the word IS. These functions let you test whether a cell is blank, has numeric content, etc.
The IS functions are Boolean functions, which means they give you a result of either TRUE or FALSE (Figure 11-9). On their own, the IS functions aren't too impressive. However, you can combine them with other conditional functions to make simple decisions. (The IF( ) function tests a condition, and then inserts one of two values based on whether the condition is true or false. For a refresher on the IF( ) function, see Section 7.1.7.)
For example, you could use the IF( ) function in combination with the ISNUMBER( ) function to avoid performing a calculation if a cell doesn't contain numeric content. Here's the formula you'd use:
=IF(ISNUMBER(A1), 10/A1, NA( ))
In this example, if the ISNUMBER( ) test returns TRUE (that is, if A1 contains a number), then Excel uses the first argument. That means the program performs the calculation 10/A1, and displays the result in the cell. If cell A1 ...