Programming paradigm for by row mapper and by column mapper

purrr_mapping_pattern.R

data(iris)

# Apply a function to rows
row_sum = function(...) {
  each_row = list(...)
  
  # call by position
  each_row[[1]] + # Sepal.Length
  each_row[[2]] + # Sepal.Width
  each_row[[3]] + # Petal.Length
  each_row[[4]]   # Petal.Width
  
  # call by column name
  each_row$Sepal.Length + 
  each_row$Sepal.Width  +
  each_row$Petal.Length +
  each_row$Petal.Width
}

iris[c("Sepal.Length", "Sepal.Width",  "Petal.Length", "Petal.Width")] %>% 
  pmap(row_sum)
  

# Apply a function to columns
col_function = function(x) {
  x + 1
}

iris[c("Sepal.Length", "Sepal.Width",  "Petal.Length", "Petal.Width")] %>% 
  map(col_function)
  
## A better approach is to use `dplyr`
iris[c("Sepal.Length", "Sepal.Width",  "Petal.Length", "Petal.Width")] %>%
  mutate_each(funs(col_function))