Extracting numbers from a string 1: Consecutive numbers at start 8

This is the first in a series of discussions on the techniques available for extracting numbers from an alphanumeric string. Since we often have many different solutions at our disposable for such tasks, I will attempt to present what I feel are the principal candidates and, for each of these set-ups, discuss the merits and potential drawbacks inherent in each.

In the next instalment in this series I shall look at extracting consecutive numbers which appear at the end of the string, e.g. ABC123. In later posts I will deal with cases in which the desired numbers to be extracted are interspersed within the string in groups of one or more, e.g. ABC12DE345-FG6H789, in which case we may be interested in extracting either the number 123456789 into a single cell or each of 12, 345, 6 and 789 into four separate cells.

I shall also consider in future posts cases in which there may be several numbers within a string, though from which we wish to extract perhaps only one (or more) of these numbers, and for which our choice of extraction is based upon one or more criteria. For example, given a string of the form X12-X34-X56-X78-X90 we may wish to develop a technique which extracts the number immediately preceding the fourth occurrence of a hyphen within that string.

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Advanced Formula Challenge #7: Results and Discussion 1

Last week I set readers the challenge which can be found here.

This is a trickier problem than it at first appears, and indeed there are several pitfalls which prevent us from using more “standard” techniques to arrive at a solution.

Perhaps the two main (hidden) obstacles, which were not immediately obvious from the examples I gave, are, firstly, the fact that we are prevented from using a construction involving a SEARCH-approach (e.g. by locating occurrences of each substring of the four types *????*, †????*, *????† and †????†, as John Jairo V attempted), since this of course presumes that there is only one occurrence of each of those substring types within our string, a presumption which cannot be made.

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