Chapter 2 Names and values

Learning objectives:

To be able to understand distinction between an object and its name
With this knowledge, to be able write faster code using less memory
To better understand R’s functional programming tools

Using lobstr package here.

library(lobstr)

Quiz

1. How do I create a new column called `3` that contains the sum of `1` and `2`?

df <- data.frame(runif(3), runif(3))
names(df) <- c(1, 2)
df
#>           1         2
#> 1 0.9442449 0.1533640
#> 2 0.5366035 0.6029954
#> 3 0.4379617 0.6630377

df$`3` <- df$`1` + df$`2`
df
#>           1         2        3
#> 1 0.9442449 0.1533640 1.097609
#> 2 0.5366035 0.6029954 1.139599
#> 3 0.4379617 0.6630377 1.100999

What makes these names challenging?

You need to use backticks (`) when the name of an object doesn’t start with a a character or ‘.’ [or . followed by a number] (non-syntactic names).

2. How much memory does `y` occupy?

x <- runif(1e6)
y <- list(x, x, x)

Need to use the lobstr package:

lobstr::obj_size(y)
#> 8.00 MB

Note that if you look in the RStudio Environment or use R base object.size() you actually get a value of 24 MB

object.size(y)
#> 24000224 bytes

3. On which line does `a` get copied in the following example?

a <- c(1, 5, 3, 2)
b <- a
b[[1]] <- 10

Not until b is modified, the third line