For loop for updating data.frame

Question

I am trying to write a "for loop" to update my R data frame by iterating.

Here is my code:

datalist = list()

for (i in 1:5) { 
dat <- data.frame(ID=LETTERS[seq( from = 1, to = 20 )],nutrition=rnorm(20, mean=50, sd=10),
                Stage=c(rep("A1",5), rep("B1",15)))
dat$ADG<-dat$nutrition*0.05
dat$M_weight<-dat$nutrition*0.5+dat$ADG*100
dat$Age<-dat$M_weight*1.1+dat$ADG*0.6
dat$Stage<-as.character(dat$Stage)
dat$Stage[dat$ADG>=3]<-"C1" 
dat$i <- i  # maybe you want to keep track of which iteration produced it?
datalist[[i]] <- dat # add it to your list    # 



}

big_data = do.call(rbind, datalist)

From iteration 2, I would like to have "Stage" updated to "C1" if ADG is equal or greater than 3 but this would not apply to iteration 1.

Thank you so much! I appreciate any replies!

Not clear what you mean. The loop is doing what it should, since the iterator i is only used in one place. If you want some dependence on the previous iteration, maybe add an if (i > 1){ do stuff with i-1 } block? — Frank
– Frank, Commented Aug 2, 2017 at 20:00
Hi @Frank. Thanks. Yes, I want somewhat dependence on the previous iteration so I will try the block you mentioned. Thanks, I appreciate your answer. — Joanna
– Joanna, Commented Aug 2, 2017 at 20:03
@Joanna your code only updates Stage based on ADG but ADG never changes. How else should the data after iteration 1 differ from the original data? — CPak
– CPak, Commented Aug 2, 2017 at 21:15
Hi, @ChiPak. Thanks for reminding and I have my code edited. Now the ADG changed every iteration but I would like to apply something from the SECOND iteration. — Joanna
– Joanna, Commented Aug 3, 2017 at 19:57

CPak · Accepted Answer · 2017-08-03 20:24:08Z

1

I think you want a recursive function instead of an iterative one

Your data stringsAsFactors=F

dat <- data.frame(ID=LETTERS[seq( from = 1, to = 20 )], nutrition=rnorm(20, mean=50, sd=10), Stage=c(rep("A1",5), rep("B1",15)), stringsAsFactors=F)

Use tidyverse for dplyr and purrr verbs

library(tidyverse)
special <- function( dat, counter, end ) { 
                 dat1 <- dat %>%
                       mutate(ADG = nutrition*0.05) %>%
                       mutate(M_weight = nutrition*0.5 + ADG*100) %>%
                       mutate(Age = M_weight*1.1 + ADG*0.6) %>%
                       mutate(Stage = ifelse( ADG >= 3, "C1", Stage )) %>%
                       mutate(i=counter)
                 if (counter < end) {
                       special(dat1, counter+1, end) 
                 } else {
                       return(dat1)
                 }                   
            }

desired <- map_df(2:5, ~special(dat,1,.x))

head(desired)

   ID nutrition Stage      ADG M_weight      Age i
1   A  47.17826    A1 2.358913 259.4804 286.8438 2
2   B  64.55988    C1 3.227994 355.0794 392.5241 2
3   C  52.29020    A1 2.614510 287.5961 317.9244 2
4   D  59.96544    A1 2.998272 329.8099 364.5899 2

Let me know if this is not the output you were expecting

answered Aug 3, 2017 at 20:24

CPak

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1 Comment

Joanna Over a year ago

Thanks @Chi Pak. Combined the "desired" and the first data frame is exactly what I want. I appreciate your help!

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