# Applying a function successively in R

At the R in Finance conference Paul Teetor gave a fantastic talk about Fast(er) R Code. Paul mentioned the common higher-order function Reduce, which I hadn’t used before.

Reduce allows me to apply a function successively over a vector.

What does that mean? Well, if I would like to add up the figures 1 to 5, I could say:

```
add <- function(x,y) x+y
add(add(add(add(1,2),3),4),5)
```

or

`Reduce(add, 1:5)`

Now this might not sound exciting, but `Reduce`

can be powerful. Here is an example with `googleVis`

. To merge two charts I use the function `gvisMerge`

, which takes two charts and wraps them up in an HTML table. Hence, to create a page with a line-, column- area- and bar chart I could use:

`pp <- gvisMerge(gvisMerge(gvisMerge(line, column), area), bar)`

or use `Reduce`

instead:

`pr <- Reduce(gvisMerge, list(line, column, area, bar))`

```
library(googleVis)
data(OpenClose)
ops <- list(legend='none', width=300, height=150)
line <- gvisLineChart(OpenClose, "Weekday", c("Open", "Close"),
options=ops)
column <- gvisColumnChart(OpenClose, "Weekday", c("Open", "Close"),
options=ops)
area <- gvisAreaChart(OpenClose, "Weekday", c("Open", "Close"),
options=ops)
bar <- gvisBarChart(OpenClose, "Weekday", c("Open", "Close"),
options=ops)
## Applying gvisMerge successively
pr <- Reduce(gvisMerge, list(line, column, area, bar))
plot(pr)
## Instead of
pp <- gvisMerge(gvisMerge(gvisMerge(line, column), area), bar)
```

### Citation

For attribution, please cite this work as:Markus Gesmann (Jul 03, 2012) Applying a function successively in R. Retrieved from https://magesblog.com/post/2012-07-03-applying-function-successively-in-r/

@misc{ 2012-applying-a-function-successively-in-r,

author = { Markus Gesmann },

title = { Applying a function successively in R },

url = { https://magesblog.com/post/2012-07-03-applying-function-successively-in-r/ },

year = { 2012 }

updated = { Jul 03, 2012 }

}