Working from the inside out, the ISNUMBER function will return TRUE when given a number and FALSE if not. When you supply a range to ISNUMBER (i.e. an array), ISNUMBER will return an array of results. In the example, the range C5:C9 contains 5 cells, so the array returned by ISNUMBER contains 5 results:
TRUE values represent numeric values.
We want to know if this result contains any TRUE values, so we use the double negative operator (--) to force the TRUE and FALSE values to 1 and 0 respectively. This is an example of boolean logic, and the result is an array of 1's and 0's:
The COUNTIF function counts cells that meet supplied criteria, returning the number of occurrences found. If no cells meet criteria, COUNTIF returns zero. Any positive number means the value was found. This means you can use the greater than...
The Excel ISNUMBER function returns TRUE when a cell contains a number, and FALSE if not. You can use ISNUMBER to check that a cell contains a numeric value, or that the result of another function is a number.
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