prog/iteration.Rmd at master · dcl-docs/prog · GitHub

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```{r include=FALSE, cache=FALSE}
set.seed(2466)

options(
  digits = 3,
  dplyr.print_max = 6,
  dplyr.print_min = 6
)

knitr::opts_chunk$set(
  cache = TRUE,
  collapse = TRUE,
  comment = "#>",
  fig.align = 'center',
  fig.asp = 0.618,  # 1 / phi
  fig.show = "hold"
)

image_dpi <- 125

# Stamps plots with a tag
# Idea from Claus Wilke's "Data Visualization" https://serialmentor.com/dataviz/
stamp <- function(
  tag = "Bad", tag_color = "#B33A3A", tag_size = 16, tag_padding = 1
)
{
  list(
    theme(
      plot.tag = element_text(color = tag_color, size = tag_size),
      plot.tag.position = "topright"
    ),
    labs(
      tag =
        str_pad(tag, width = str_length(tag) + tag_padding, side = "left")
    )
  )
}

```

# (PART) Iteration {-}

# Introduction

It's often useful to apply the same function to every element of a vector, list, or tibble. The purrr package contains a set of useful functions for iterating over data structures and performing the same action at each element. In this section, we'll introduce some of the most useful purrr functions and explain how to apply them in different situations.