Creating a loop in R to avoid repetitive code

Question

I am trying to get my head around using loops in R so that I can avoid the repetitive code I used to format a table.

I'm just starting the process of learning loops to automate tasks, so there's been mostly blank stares up to this point. The long version of the code I used does the job, but wouldn't be practical on a larger scale.

library(DT)

##  Create data frame containing test results for Students A - H.   
A <- c(69, 64, 70, 57, 80, 34, 45, 56, 96)
B <- c(70, 74, 68, 76, 71, 56, 56, 45, 30)
C <- c(84, 58, 87, 78, 67, 67, 43, 34, 56)
D <- c(78, 83, 68, 72, 90, 48, 23, 23, 46)    
E <- c(79, 55, 91, 71, 34, 26, 76, 67, 75)    
F <- c(80, 72, 64, 45, 66, 76, 45, 56, 54)    
G <- c(90, 67, 76, 51, 45, 59, 33, 64, 34)    
H <- c(60, 59, 88, 90, 76, 34, 43, 72, 45)    
student_results <- data.frame(A, B, C, D, E, F, G, H)   

##  Create table of data frame, highlighting marks >= 85 in 'aquamarine'
##  Marks < 50 highlighted in 'coral'
datatable(student_results) %>%      
  formatStyle('A',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('B',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('C',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('D',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('E',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('F',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('G',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))) %>%      
  formatStyle('H',
              backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine"))

The code I came up with does the job but is very repetitive. I've been trying to figure out how to either get a loop to run the formatStyle() function over every column in the table, or find some other function that performs the same task, but haven't had any success.

What package does datatable and formatStyle come from?

Spacedman
– Spacedman

2019-02-05 11:42:01 +00:00
Commented Feb 5, 2019 at 11:42 — Spacedman
– Spacedman, Commented Feb 5, 2019 at 11:42

A. Suliman · Accepted Answer · 2019-02-05 11:44:44Z

2

library(DT)
#colnames(student_results)[2:ncol(student_results)] #if you need selected columns
datatable(student_results) %>% 
          formatStyle(colnames(student_results),backgroundColor = styleInterval(c(50,85), c("coral", "white", "aquamarine")))

answered Feb 5, 2019 at 11:44

A. Suliman

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1 Comment

ARH Over a year ago

And this is even simpler than what I was looking for, thanks again!

Spacedman · Accepted Answer · 2019-02-05 11:46:40Z

0

Piping a %>% b() %>% b() %>% b() is the same as repeatedly evaluating b(b(b(a))), so your for loop version would look like repeated applications of your function:

> sr = datatable(student_results)
> for(L in LETTERS[1:8]){
     sr = formatStyle(sr, L, 
          backgroundColor = styleInterval(
              c(50,85), c("coral", "white", "aquamarine")))}
> sr

answered Feb 5, 2019 at 11:46

Spacedman

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