Nested for-loop with if statement

Question

This is the code that I am trying to run and it's taking a while.

Districts is a data frame of 39299 rows and 16 columns and lm_data is a data frame of 59804 rows and 16 variables. I want to set up a new variable in lm_data called tentativeStartDate which takes on the value of districts$firstDay[j] if a couple of conditions are meant. Is there a more efficient way to do this?

for (i in 1: nrow(lm_data)){
  for (j in 1: nrow(districts)){
    if (lm_data$DISTORGID[i] == districts$DISTORGID[j] & lm_data$gradeCode[i] == districts$gradeCode[j]){
      lm_data$tentativeStartDate[i] = districts$firstDay[j]
    }
  }
}

Please provide a minimal reproducible example. See How to make a great R reproducible example? for what this would mean in R. Also, as a new user, it wouldn't hurt for you to take the tour and read How to Ask. — John Coleman
– John Coleman, Commented Jun 25, 2021 at 15:12

Snipeskies · Accepted Answer · 2021-06-25 15:46:55Z

1

Not sure if this will work since I can't test it, but if it does work it should be much faster.

# get the indices
idx <- which(lm_data$DISTORGID == districts$DISTORGID & lm_data$gradeCode == districts$gradeCode)

lm_data$tentativeStartDate[idx] <- districts$firstDay[idx]

answered Jun 25, 2021 at 15:46

Snipeskies

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