Performing calculations in the spreadsheet
If you select a cell in the spreadsheet that already contains information, then overwrite it with new information, the existing information in the spreadsheet is overwritten by the new information. For example, if the Duration column displays 20d for a task, and you select it and overwrite it with '15d'- replacing the existing data in the cell - the task’s duration changes to 15d.
However, as well as entering figures into the spreadsheet directly, you can use a number of mathematical operators to perform calculations with figures in the spreadsheet.
To add to, subtract from, multiply by or divide by existing information in the spreadsheet, prefix the information you enter with the +, -, * or / operator. For example, if the Duration column displays 20d for a task, and you select it and overwrite it with '+15d', the task’s duration changes to 35d (15d is added to the duration). If you select it and overwrite it with '/2', the task’s duration changes to 10d (the duration is divided by 2).
You can also add and subtract percentages, by adding the % suffix to the information you enter. For example, if the Cost column displays £20 for a task, and you select it and overwrite it with '–10%', the task’s cost changes to £18 (10% is subtracted from the cost). If you select it and overwrite it with '+50%', the task’s cost changes to £30 (50% is added to the cost).
Note that if you have a negative financial figure, for example £-30, you cannot subtract from it using the – operator; this will simply overwrite the original figure with the new figure you enter.
As well as displaying a wide range of fields in spreadsheet columns, you can construct formulae - user-calculated expressions - that define precisely what information is displayed in a spreadsheet column. You can construct formulae to display practically any information in the spreadsheet: formulae can reference spreadsheet fields, user-defined fields and tables, variable dates, etc, and can take information from the live data or from a specified baseline. On top of this, you can construct formulae to perform calculations on project data. For example, you could construct a formula to subtract the baseline cost from the actual cost in the live data, then display the result in a format of your choosing; you could construct a formula to calculate what percentage of total project costs the cost of each individual task represents.