We put a lot of effort into our free spreadsheet tools. We want our spreadsheets to be usable by anyone who needs an answer to their questions. Some good practices have become common in our tools and we want to share them with you as well.
No Macros or Add-Ins
A lot of what we do would be easier if we used Excel macros or add-ins. We resist the urge to do this. By including macros or add-ins we are shipping code and Excel gives all manner of warnings to the user that the spreadsheet may be a security risk. It also inhibits the spreadsheets being compatible on Google Sheets. We haven’t needed to use macros, and compete feature for feature against many paid add-ins. We are extremely proud to be performing Monte Carlo simulation and distribution fitting algorithms using plain formulas that YOU can see. Nothing is hidden. But gee, a lot of sleepless nights in this goal…
Title and Read me worksheet
Always have a title page worksheet that describes the spreadsheets intention, and who and how to contact us with ideas for improving them. Document the main steps in getting a result. Some of our spreadsheets are four or five worksheets deep and we want to avoid people becoming immediately lost in the appropriate workflow.
Data entry is by offset reference
Initial versions of our spreadsheets had a column for user data to be populated. What we found we needed was the ability to copy, paste, drag, delete, manipulate this data in the spreadsheet directly. However, whenever a column or cell was moved, our formulas referencing those cells broke. We solved this problem by using an indirect reference to “duplicate” the user data on another worksheet using Excel’s INDEX function, for example:
This formula references another cell by row number, and the row number doesn’t change with any user action you can do with the clipboard, dragging or manipulation. We write all formulas against the indirect copy of the original data in a worksheet commonly called “Calculations”. We copy down the formula as shown, where the A2 will be a series, A3, A4, A5 …
We standardized on a worksheet called “Your Data” which no formula every directly references. We find ourselves dragging columns of different data into this sheet and everything keeps just working.
Column References and Capacity Growth
No matter how big we make the spreadsheets support input data, someone always emails wanting more. We structure our formulas now to limit the places where an absolute row count is needed. Here are the ways we tackle this –
- Use column references A:A rather than A2:A5000 in formulas wherever possible
- Use names ranges, Formulas-Name Manager to define names for ranges. We use the names in formulas where possible
- When we need to handle a date range, we do 250 weeks or 5,000 day dates individually
- We always set the background color of a formula cell to the calculation cell type, so we can visually see where we stopped copying a formula row down. We also try and put a comment at that point saying how the user can expand it.
Top Left to Bottom Right Flow
We design our worksheets to be read and populated from the top left to bottom right. We also try and number each input sell title, and add a tip nearby. When we get a question we try and add more documentation to these tips. We would love feedback on where people get stuck. This is pretty standard user design guidelines.
Auto Chart Axis Growth & Shrink
A very hidden feature we utilize is how the charts automatically grow and shrink the axis values to match your specific data. By default, you specify a pre-determined range for chart data, but we don’t know in advance how many days or weeks your data contains. To auto-grow/shrink, we use a named cell range that starts at the first row of data for the column being chosen, and stops at the last row with valid data (not blank or zero is the normal rule). We bind this named range to the chart axis, and Excel takes care of the rest. For example, for cycle time a range formula CycleTimeRange is defined as –
This decodes to a range Calculations!L2:Lx where x is the last row before any zero date (excel counts empty dates as a zero integer value, we just know this by experimentation). In any chart data series, you reference this range like this (it has to be fully qualified) –
='Throughput and Cycle Time Calculator (5000 samples).xlsx'!CycleTimeRange
This technique allows us to handle any amount of user data and have the charts auto-resize. Its a little cumbersome to get working, but works great one you get it right.
Documenting Complex Formulas
On our more complex calculation sheets we try and add a not about each formula and how it works. Nothing is hidden in the formula bar, but some aren’t even clear to us after we have written and debugged them the first time.
We continually learn new things, and will post more tips over time. Please give us feedback on what we can do to make these spreadsheets easier to use.