By civilstat

**Civil Statistician » R**, and kindly contributed to R-bloggers)

I’ve seen R users swooning over the `magrittr`

package for a while now, but I couldn’t make heads or tails of all these scary `%>%`

symbols. Finally I had time for a closer look, and it seems potentially handy indeed. Here’s the idea and a simple toy example.

So, it can be confusing and messy to write (and read) functions from the inside out. This is especially true when functions take multiple arguments. Instead, `magrittr`

lets you write (and read) functions from left to right.

Say you need to compute the LogSumExp function , and you’d like your code to specify the logarithm base explicitly.

In base R, you might write`log(sum(exp(MyData)), exp(1))`

But this is a bit of a mess to read. It takes a lot of parentheses-matching to see that the `exp(1)`

is an argument to `log`

and not to one of the other functions.

Instead, with `magrittr`

, you program from left to right:`MyData %>% exp %>% sum %>% log(exp(1))`

The pipe operator `%>%`

takes output from the left and uses it as the first argument of input on the right. Now it’s very clear that the `exp(1)`

is an argument to `log`

.

There’s a lot more you can do with `magrittr`

, but code with fewer nested parentheses is already a good selling point for me.

Apart from cleaning up your nested functions, this approach to programming might be helpful if you write a lot of JavaScript code, for example if you make D3.js visualizations. R’s `magrittr`

pipe is similar in spirit to JavaScript’s method chaining, so it might make context-switching a little easier.

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