Once a cell is selected, you can tap-and-drag on one of its corners to expand the selection to a range; you can then move that range (or a cell) with a tap-and-hold operation. You can also bring up a contextual menu of sorts, by tapping on a cell that's already selected (i.e. highlighted on the worksheet). This brings up a bar from which you can cut, copy, clear, fill, or wrap the cell. If you choose Fill, the cell gains small arrows on its right and bottom sides, and you can then drag those arrows to fill adjacent cells, as you can do in the desktop version of Excel.
Microsoft did an incredible job at getting a lot of Excel's power into the iPad version of the app. There are over 400 formulas present — if that's not all of the formulas from the desktop version, it's the vast majority of them. Most of the chart types have also migrated, and creating a chart is as easy as selecting the data to chart, tapping the Insert ribbon, choosing a chart type, and then tap-dragging out a region for the chart.
You can also choose from a large assortment of shapes, add text boxes, and even insert images. However, the image browser is restricted to photos stored on the iOS device; you can't access any media files on your OneDrive, for example. The help system is relatively complete, including a comparison table that shows what you can do in each version of Excel (iOS, OS X, Windows), along with a touch guide that explains how to interact with your data.
From functions to fonts to cell borders to merging cells to table styling to hiding and shuffling worksheets in a workbook, Excel for iPad has most of the features of the desktop version. Some are limited, of course — there aren't nearly as many cell border styles — but there's enough here to meet the needs of even heavy-duty spreadsheet users. I was impressed with the responsiveness of the app, even when working on somewhat larger worksheets — scrolling was smooth, and I didn't notice any slowdowns or other issues.
Things to be aware of
There are some features missing from Excel for iPad. Many people have noted the inability to print — if you want to print your worksheets, you'll need to find a Windows or OS X computer to do so. (You may be able to open a spreadsheet in Numbers and print it that way, too.) This may or may not be a big issue, depending on your workflow.
As noted earlier, you can't create comments; you also can't name cells or ranges (but you can work with existing names), nor create conditional formatting rules. Existing array formulas work, but you can't enter or create new ones. You can see existing sparklines (a full graph in one cell, basically), but you cannot create new ones. Finally, references in formulas to cells on external worksheets won't update.
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