The single-greatest difference?
R and Excel are both powerful tools for the analyst. A good analyst uses each when appropriate.
Many analysts haven’t used R, for different reasons. For one, it has a steeper learning curve than Excel. It is also less likely to be used by your boss.
But it is a very powerful tool.
There are some real differences between the two. Perhaps the single-greatest is the assignment of variables in R.
When writing a formula in Excel, we point-and-click on a cell to reference, and Excel will write the cell reference for us (e.g., cell A1, column B, range C1:D4, etc).
In R, we need to name everything we will reference.
In the below example, I perform a simple function (summing 2, 1, and 6; Cleveland’s area code!) in both R and Excel.
Notice that in Excel I just drop each number into a cell, grab another cell, and sum them.
It’s not actually less than…
In R, I assign these numbers to a vector, then sum.
I do this with the symbol “<-“. This takes some getting used to; think of it as a reverse arrow pointing your expression to the variable.
You can technically use “=” instead of “<-“. If this notation makes you more comfortable as an Excel user in the early days of learning R, go for it. But programmers nearly universally use the “<-” notation.