选择具有多个 if 和 if else 语句的行 (R)

Question

I tried to solve the following problem with if and else if statements:

1. If "TRUE1" is apparent in column "check" select rows with "TRUE1"
2. If "TRUE1 is not apparent in column "check" select rows with "TRUE2" else rows with "TRUE3"

The below code seems to work fine when "TRUE1" and "TRUE2" are available in column "check":

name <- c(1, 2, 3, 4, 5)
check <- c("TRUE1", "TRUE2", "TRUE3", "TRUE3", "TRUE3")
dataset <- data.frame(cbind(name, check))

> dataset
  name check
1    1 TRUE1
2    2 TRUE2
3    3 TRUE3
4    4 TRUE3
5    5 TRUE3

slct_set <- if (dataset$check == "TRUE1") {
  dataset[dataset[, "check"] == "TRUE1",] 
} else if (dataset$check != "TRUE1") {
  dataset[dataset[, "check"] == "TRUE2",]
} else {
  dataset[dataset[, "check"] == "TRUE3",]
}

> slct_set
  name check
1    1 TRUE1

However, when I use "TRUE3" for the whole column "check" this happens:

> dataset
  name check
1    1 TRUE3
2    2 TRUE3
3    3 TRUE3
4    4 TRUE3
5    5 TRUE3

> slct_set <- slct_set <- if (dataset$check == "TRUE1") {
  dataset[dataset[, "check"] == "TRUE1",] 
} else if (dataset$check != "TRUE1") {
  dataset[dataset[, "check"] == "TRUE2",]
} else {
  dataset[dataset[, "check"] == "TRUE3",]
}

Warning messages:
1: In if (dataset$check == "TRUE1") dataset[dataset[, "check"] == "TRUE1",  :
  the condition has length > 1 and only the first element will be used
2: In if (dataset$check != "TRUE1") dataset[dataset[, "check"] == "TRUE2",  :
  the condition has length > 1 and only the first element will be used

> slct_set
[1] name  check
<0 Zeilen> (oder row.names mit Länge 0)

I am quite new to if statements in R, so any help is appreciated.

Answer 1

You could try something like the following code, where test is the vector according to which you would like to subset your dataframe (in descending priority):

name <- c(1, 2, 3, 4, 5)
check <- c("TRUE1", "TRUE2", "TRUE3", "TRUE3", "TRUE3")
dataset <- data.frame(cbind(name, check))

test <- c("TRUE1", "TRUE2", "TRUE3")
dataset[dataset$check == test[min(which(test %in% dataset$check))],]
#>   name check
#> 1    1 TRUE1

A little explanation to the code above: test %in% dataset$check checks if the elements of the test vector appear in the check column of dataset . which() returns the positions in the resulting vector, which evaluate to TRUE . min() therefore returns the very first element of test which is existing in the column to check. The rest is just subsetting. Maybe a bit more straghtforward than a nested if else.

^{Created on 2020-07-20 by the reprex package (v0.3.0)}

Answer 2

Maybe you should use %in% for the condition of if...else... like below

if ("TRUE1" %in% dataset$check) {
  dataset[dataset[, "check"] == "TRUE1",] 
} else if ("TRUE2" %in% dataset$check) {
  dataset[dataset[, "check"] == "TRUE2",]
} else {
  dataset[dataset[, "check"] == "TRUE3",]
}

Answer 3

Using %in% to check if the column contains the text would be the first step. The (if that condition is satisfied) you return the relative filtered dataset

name <- c(1, 2, 3, 4, 5)
check <- c("TRUE1", "TRUE2", "TRUE3", "TRUE3", "TRUE3")
dataset1 <- data.frame(cbind(name, check))
check <- c("TRUE2", "TRUE2", "TRUE3", "TRUE3", "TRUE3")
dataset2 <- data.frame(cbind(name, check))
check <- c("TRUE3", "TRUE3", "TRUE3", "TRUE3", "TRUE3")
dataset3 <- data.frame(cbind(name, check))


func_name = function(dataset){
  if("TRUE1" %in% dataset$check){
    dataset[dataset$check == "TRUE1",]
  }
  else if("TRUE2" %in% dataset$check){
    dataset[dataset$check == "TRUE2",]
  }
  else if("TRUE3" %in% dataset$check){
    dataset[dataset$check == "TRUE3",]
  }
  else{
    "none found"
  }
}

func_name(dataset = dataset3)

  name check
1    1 TRUE3
2    2 TRUE3
3    3 TRUE3
4    4 TRUE3
5    5 TRUE3