CODEWITHSUNDEEP
r
hihowareyouihaveaquestion
hihowareyouihaveaquestion

Reputation: 13

Change values in a column based on a condition

I have to add a specific number of character to the end of a value inside of a character vector under a condition - only for a certain columns. Each value has to have a fixed length of 5 characters, and if current value has less then 5, I have to add zeroes until it reaches maximum length - only if the first character of a value is a ie. letter "A". 

input_vector <- c("ABC", "ZZX", "B", "AILK") 
desirable_output <- c("ABC00", "ZZX", "B", "AILK0")

I am fairly new to the R world and I've only tried to write clunky code such as this one:

example_df<- data.frame(Col1= 1:11, Col2= 2:22, Col3= 3:33, Col4= 6:66)
index_values_of_columns<- c(1, 2, 4)
for (index_value in index_values_of_columns){
  for (value in example_df[[index_value]]){
    firstletter<-str_extract(value, "^.{1}")
    if (!is.na(firstletter) && firstletter == "1"){
      value<-str_pad(value, 5, side="right", pad="0")
    }
  }
}

Unfortunately, this doesn't change anything in a dataframe, although it doesn't generate any errors. Where I did wrong?

Upvotes: 1

Views: 150

Answers (2)

Daniel O
Daniel O

Reputation: 4358

Here is a solution in base R

replace(input_vector,grep("A.",input_vector),strtrim(paste0(input_vector,"00000"),5)[grep("A.",input_vector)])

Upvotes: 0

Sotos
Sotos

Reputation: 51582

Try,

input_vector[substring(input_vector, 1, 1) == 'A'] <- str_pad(input_vector[substring(input_vector, 1, 1) == 'A'], 5, side = "right", pad = "0")
input_vector
#[1] "ABC00" "ZZX"   "B"     "AILK0"

Upvotes: 2

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