Looping Functions in R

[omario]

I have the following data in R:

#PART 1
#create data

library(dplyr)
library(caret)
set.seed(123)



salary <- rnorm(1000,5,5)
height <- rnorm(1000,2,2)
my_data = data.frame(salary, height)

I created the following loop - but for some reason it only saves the final iteration:

for (i in 1:10)
    
{
    
    
    #PART 2
    #create train_i and test_i data
    
    
    train_i<-sample_frac(my_data, 0.7)
    sid<-as.numeric(rownames(train_i)) 
    test_i<-my_data[-sid,]
    
    #PART 3
    salary_quantiles = data.frame( train_i %>% summarise (quant_1 = quantile(salary, 0.33),
                                                          quant_2 = quantile(salary, 0.66),
                                                          quant_3 = quantile(salary, 0.99)))
    
    
    
    
    #PART 4
    train_i$salary_type = as.factor(ifelse(train_i$salary < salary_quantiles$quant_1 , "A", ifelse( train_i$salary  >  salary_quantiles$quant_1  & train_i$salary < salary_quantiles$quant_2, "B", "C")))
    
    #PART 5
    height_quantiles = data.frame( train_i %>%  group_by(salary_type)  %>%  summarise(quant_80 = quantile(height, 0.80)))
    
    
    
    #PART 6
    #test_i
    
    test_i$salary_type = as.factor(ifelse(test_i$salary < salary_quantiles$quant_1 , "A", ifelse( test_i$salary  >  salary_quantiles$quant_1  & test_i$salary < salary_quantiles$quant_2, "B", "C")))
    
    test_i$height_pred <- height_quantiles$quant_80[match(test_i$salary_type, height_quantiles$salary_type)]
    
    test_i$accuracy = ifelse(test_i$height_pred > test_i$height, 1, 0)
    
    #PART 7 : Results Frame
    
    results_i = data.frame(test_i %>%
                               group_by(salary_type) %>%
                               dplyr::summarize(Mean = mean(accuracy, na.rm=TRUE)))
    
    results_i$iteration = i
    
    results_i$total_mean = mean(test_i$accuracy)
    
}

Here are the results from this loop (only the final iteration was saved, i.e. iteration = 10)

> results
  salary_type      Mean iteration total_mean
1           A 0.7582418        10  0.7566667
2           B 0.7818182        10  0.7566667
3           C 0.7272727        10  0.7566667

Can someone please show me how to fix this?

Thanks!

[technocrat]

Because results is created within the loop anew with every iteration only its state the last time through is preserved. The fix is to create an appropriate holder object in the global environment before the loop and use that to accumulate the results of each iteration.

[Stargazer_ch]

Agree with @technocrat - to be more specific, results_i does NOT expand to results_1, results_2, ....

You could put results into a list of dataframes for example

Just before the for loop, insert

results <- list()

and then change any occurrence of results_i into results[[i]] after which all 10 results will be listed in results as expected.