Condition to exit a loop in R

Question

I want to write a function to change the median by touching minimum number of elements in my data. My data is as follows,

data = data.frame(name=letters, values = c(0.183487333,0.487690292, 0.510321455,0.616632727, 0.660789818, 0.845322255, 0.867910555, 0.911842909, 0.913312571, 1.017638286, 15.97454546, 16.20765382, 16.27542982, 16.307264, 17.38325527, 17.54139927, 70.08443928, 70.26106764, 75.79405382, 77.72412946, 79.58750724, 84.67373672, 87.04692364, 88.58626037, 94.79392582, 100.0000))
data = data %>% mutate(diff = abs(values - median(values)), rank_diff = dense_rank(diff)) %>% arrange(diff)

and below is my function,

changemedian <- function(data, increase, rows) 
{
  median2 = median(data$value)
  new_median = median2 + increase
  i = 0
  print(data$name[1:rows])
  data1 = data$values
  while(median2<new_median){
    x = median2
    data1[1:rows] = data1[1:rows] + 0.2
    median2 = median(data1)
    i = i + 0.2
  }
  print(paste("values to be changed per name:",i))
  cat("\n")
  print(paste("New Median that could be achieved:" ,median2))
}

I can call this function when I want to increase the median by 1 and I want to use only 5 values to do it by changemedian(data,1,5). The code is working fine for this. But when I give a improbable condition when the median can't be achieved like changemedian(data,1,1), the loop keeps on running. I want to loop to exit when the median is equal to previous median value. Here when median2 is equal to median2 value during the previous loop, I want to exit the loop by saying "not possible".

I am getting errors to do this. Can anybody help me in doing this?

Thanks

Does this answer your question? [R: Break for loop](https://stackoverflow.com/questions/6082655/r-break-for-loop) — iacob, Oct 30 '21 at 11:47

R.S. · Accepted Answer · 2016-03-29T18:44:27.293

4

I think what is happening is this -- In case of changemedian(data,1,1), we are only incrementing the first element, which is already greater than the median. So the median does not change on increasing it , and the loop never stops. The median increases only when you increment some numbers smaller than the median.

Edit: To exit the loop if a median is repeated add this line :

if  ( median(data1) == median2 ) break;

just before the line

median2 = median(data1);

edited Mar 29 '16 at 18:44

answered Mar 29 '16 at 18:35

R.S.

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yes I just want to exit the loop when that happens. Can you help me in exiting the loop. I am facing errors with that. If median value for two loops are equal, I want to exit the loop. – haimen Mar 29 '16 at 18:36
I only want to exit the loop giving some statement not possible. That is where I am struggling – haimen Mar 29 '16 at 18:38
Thanks for this. I tried this. But still the last two print statements are printed. I want to print it only when it is satisfied. When I move this into loop, it is printing every iteration. that is the problem i am facing – haimen Mar 29 '16 at 18:50
In that case, use `return` instead of `break` – R.S. Mar 29 '16 at 18:51
Thanks. This is working 70-80%. I think I can still edit others and make it workable. – haimen Mar 29 '16 at 19:07
wishing you the best. – R.S. Mar 29 '16 at 19:08
Look into the `stop` function. For example `if ( median(data1) == median2 ) stop('Error Message');` – Jacob H Mar 29 '16 at 19:31

Condition to exit a loop in R

1 Answers1