1.3 Introduction to Summary Areas
In the model under discussion, cell C4 contains the SUM function that calculates the total revenues for the years 1 through 5:
This summary figure provides an easy-to-read value for the total of the revenues in the forecast:
Note that the inputs to the function in cell C4 is to the left of the data that it summarises (i.e. the values in the range H4:L4), and therefore does not respect the “principle” of using left-to-right flow in Excel modelling. Nevertheless, such an approach (which compromises this principle) can be valuable because the alternatives (such as placing the summary calculation to the right i.e. in columns M or N) would typically be less transparent, as well as being error prone. For example, a formula in cell M4 could easily be overwritten by accident if using a short-cut to copy into an existing range of formulas, such as Ctrl+Shift+Right Arrow), and – especially in a large model with many time periods – the presence of such summary items may not be clearly visible to a user.
Of course, there are many possible variations as well as much more complex uses of summary areas: For example, in larger models, there may be several summary areas, or a single central summary (reporting) areas. Similarly, in models with columnar structures, such as databases, it can sometimes be useful to create summary figures in the first row above the data set (as shown in other examples).