R 循环遍历数据帧并使用条件迭代地创建新数据帧

Question

I am looking for a method to loop through a data frame in R, removing the max value above a specific condition, creating a new data frame excluding that row, re-calculating the values & running iteratively until there are no more rows above a specific condition - with the output excluding all of the rows removed. Here is a simple dataset (I need it step by step because the values change at each time of iteration with the data I work with). The condition for this example would be when df$ratio > 1.9.

height <- c(100, 110, 105, 130, 160, 150, 140, 145)
bodymass <- c(60, 65, 66, 75, 90, 85, 70, 72)
df <- data.frame(height, bodymass)
df$ratio <- df$height / df$bodymass

For this data there would be the following kind of iterations;

-> df$ratio <- df$height / df$bodymass
-> df$ratio > 1.9 #Condition
-> Calculate max df$ratio in df > 1.9 #first loop would remove 2.013
-> Create new df excluding that value #Now loop back to start 
-> df$ratio <- df$height / df$bodymass #Recalculate (This is really important)
-> df$ratio > 1.9 #Condition
-> Calculate max df$ratio in df > 1.9 #second loop would remove 2.000
-> Create new df excluding that value #Now loop back to start 
-> df$ratio <- df$height / df$bodymass #Recalculate (This is really important)
-> df$ratio > 1.9 #Condition - none left now so can exit the loop.
-> output df excluding values > 1.9.

The recalculation is the most important step in this really. I can do this manually no problem but have datasets with thousands of rows so needs to be automatic. Any help would be greatly appreciated. Thank you.

Answer 1

You can try using while loop:

#Calculate initial ratio
df$ratio <- df$height / df$bodymass

#Continue while loop till any value is above 1.9
while(any(df$ratio > 1.9)) {
  #Remove the row with max ratio
  df <- df[-which.max(df$ratio), ]
  #Recalculate ratio
  df$ratio <- df$height / df$bodymass
}