在 R 中循环通过 DataFrame

Question

Some of you might recognise the example below as I have asked a few questions on it (Thank you for your support - I am still trying to learn R and the syntax!)

What I want to do is loop through the entries of a for loop - I want to check if the average is not equal to the sum of BDA and DAD. I know I can just run the line above the for loop which will do it, but I'm trying to figure out how to access elements of the DataFrame individually. I am getting an error with the below code (I appreciate there's some redundant code here - I am just playing around with it!)

DAD <- c(80, 65, 50)
BDA <- c(70, 50, 80.4)

gender <- as.factor(c("F", "M", "M"))
nationality <- as.factor(c("IRL", "UK", "IRL"))
age <- c(20, 21, 22)

age <- as.integer(age)
DAD <- as.integer(DAD)
BDA <- as.integer(BDA)

student <- data.frame(name, age, gender, nationality, DAD, BDA)

#student$average <- as.double(as.double(student$BDA) + as.double(student$DAD))/2
#The above will do what I want if placed before the for loop, but I want to #figure it out 

student <- rbind(student, c("Dennis", 23, "M", "UK", 55, 70))

student <- rbind(student, c("Bennis", 23, "M", "UK", 55, 70, NA)) 

for (row in 1:nrow(student)) {
  avg = (as.double(student[row]$BDA) + as.double(student[row]$DAD))/2
  print(avg)
  if(as.double(student[row]$average) != avg) { 
    student[row]$average = (student[row]$BDA + student[row]$DAD)/2
    }  

Answer 1

I'm not sure why you want to use a for -loop. But your elements inside your for -loop do not depend on row which is the iteration variable of your loop. Therefore your loop should look something like this:

  for (row in 1:nrow(student)) {
    avg[row] = (as.double(student$BDA[row]) + as.double(student$DAD[row]))/2
    print(avg[row])
    if(as.double(student$average[row]) != avg[row]) { 
      student$average[row] = (student$BDA[row] + student$DAD[row])/2
    }  
  }