How to apply a formula to all rows without for loop in R?

Question

I have a column with values as follows and I want to take 1 random value between "+or_"20% of the same value of each row and assign it to another column.

sample_data

Now I want to create a variable called value in the same data by adding 1 random number between +or- 20% of the benchmark value for each row.

Expected output:

    benchmark   value
 1  100         87 
 2  200         213
 3  250         255
 4  400         320
 5  150         180
 6  1000        900

The snippet below illustrates my attempt to achieve that; it works as expected, but takes too much time to get executed:

for (i in 1:nrow(sample_data)){
    sample_data$value[i] = sample_data$benchmark[i] + runif(1,min = -0.2*sample_data$benchmark[i], max = 0.2*sample_data$benchmark[i])
}

How can I improve upon the performance of my code?

989 · Accepted Answer · 2017-05-28 17:15:35Z

5

How about:

sample_data$value <- runif(length(sample_data$benchmark), 
                            min = 0.8 * sample_data$benchmark, 
                            max = 1.2 * sample_data$benchmark)

edited May 28, 2017 at 17:15

989

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answered May 28, 2017 at 15:02

Constantinos

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2 Comments

Surendra babu Pasumarhti Over a year ago

please try to understand the question.... the code u suggested me will generate n row of samples.... which is of no use... any how thanks

Constantinos Over a year ago

The code will generate 1 random value between 80% and 120% of the benchmark value in the same row. I believe it gives exactly what you have asked for.

Vasim · Accepted Answer · 2017-05-28 15:24:09Z

1

library(dplyr)
sample_data %>% mutate(value = benckmark + (benckmark * runif(1, -0.20, 0.20)))

Tested on

sample_data <- tribble(~Benckmark, 100, 200, 250)

answered May 28, 2017 at 15:24

Vasim

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