Dynamic column name in for loop

Question

I have problem with my code. I have data frame like this:

A <- c(21, 234, NA, 286,NA)
B <- c(3,NA,NA, 8, 10)
data <- data.frame(A,B)
data

    A  B
1  21  3
2 234 NA
3  NA NA
4 286  8
5  NA 10

And the effect I want to create is:

    A  B A_NA B_NA
1  21  3    0    0
2 234 NA    0    1
3  NA NA    1    1
4 286  8    0    0
5  NA 10    1    0

Here is my simple code, but something doesn't work..

for(i in c(1:ncol(data)))
  {
    data[, ncol(data) + 1] <- ifelse(is.na(data[i]), 1, 0)
    names(data)[ncol(data)] <- paste0(colnames(data[i]), "_NA")
  }

because effect is:

    A  B A A B A A
1  21  3 0 0 0 0 0
2 234 NA 0 0 1 0 0
3  NA NA 1 1 1 0 0
4 286  8 0 0 0 0 0
5  NA 10 1 1 0 0 0

akrun · Accepted Answer · 2017-06-27 10:13:52Z

2

We can use lapply to loop over the columns of 'data', check whether the elements are NA (is.na(x)), convert to integer (as.integer) and assign the output to new columns

data[paste0(names(data), "_NA")] <- lapply(data, function(x) as.integer(is.na(x)))
data
#    A  B A_NA B_NA
#1  21  3    0    0
#2 234 NA    0    1
#3  NA NA    1    1
#4 286  8    0    0
#5  NA 10    1    0

answered Jun 27, 2017 at 10:13

akrun

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Comments

amonk · Accepted Answer · 2017-06-27 13:21:12Z

0

Adding columns based on a condition:

 data$A_NA<-ifelse(is.na(data$A),1,0)
 data$B_NA<-ifelse(is.na(data$B),1,0)

addition

Recursively:

for(nm in names(data))
  eval(parse(text = paste0("data$",nm,"_NA<-ifelse(is.na(data$",nm,"),1,0)")))

addition2

Alternatively one can use:

for(nm in names(data)){
  assign(paste0(nm,"_NA"), ifelse(is.na(data[nm]),1,0))
  tempo<-data.frame(get(paste0(nm,"_NA")));names(tempo)<-paste0(nm,"_NA")
  data<-cbind(data,tempo)
}

edited Jun 27, 2017 at 13:21

answered Jun 27, 2017 at 10:21

amonk

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2 Comments

little girl Over a year ago

Yes, but i have 1000 columns and in this case need loop

thelatemail Over a year ago

Nothing necessarily wrong with a for loop for this sort of task, but there is little need for eval + parse - e.g.: for(nm in names(data)) { data[paste0(nm,"_NA")] <- as.integer(is.na(data[nm]))}

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