CODEWITHSUNDEEP
r
Nathan123
Nathan123

Reputation: 763

how to store the printed output from a function as a vector in R?

I have the following column from a dataframe

df <- data.frame(
 crime = as.character(c(115400, 171200, 91124, 263899, 67601, 51322)),
 stringsAsFactors=FALSE
)

I am using a function to extract the first two digits based on some condition as seen on the function below

for (i in df$crime){
  if (nchar(i)==6){
    print(substring(i,1,2))}
  else {print(substring(i,1,1))
  }
}

when I run this function I get the following output which is what I want

[1] "11"
[1] "17"
[1] "9"
[1] "26"
[1] "6"
[1] "5"

However, I want this to be saved as stand along vector. how do I do that?

Upvotes: 1

Views: 809

Answers (4)

PavoDive
PavoDive

Reputation: 6486

I can imagine some situations where keeping the extracted codes within the original data frame is useful.

I'll use the data.table package as it's fast, which may be handy if your data is big.

library(data.table)

# convert your data.frame to data.table
setDT(df)

# filter the rows where crime length is 6,
# and assign the first two characters of
# it into a new variable "extracted".
# some rows now have NAs in the new
# field. The last [] prints it to screen.
df[nchar(crime) == 6, extracted := substring(crime, 1, 2)][]

Upvotes: 0

Ronak Shah
Ronak Shah

Reputation: 388807

Using regex : 

output <- with(df, ifelse(nchar(crime) == 6, sub("(..).*", "\\1", crime), 
                                             sub("(.).*", "\\1", crime)))
output
#[1] "11" "17" "9"  "26" "6"  "5"

It becomes a little simpler with str_extract from stringr

with(df, ifelse(nchar(crime) == 6, stringr::str_extract(crime, ".."),
                                   stringr::str_extract(crime, ".")))

Upvotes: 0

ThomasIsCoding
ThomasIsCoding

Reputation: 101034

Here is a base R solution with ifelse+ substring

res <- with(df, substring(crime,1,ifelse(nchar(crime) == 6, 2, 1)))

such that

> res
[1] "11" "17" "9"  "26" "6"  "5"

Upvotes: 2

akrun
akrun

Reputation: 886938

substr/substring are vectorized, so we can use ifelse

v1 <- with(df1, ifelse(nchar(crime) == 6, substr(crime, 1, 2), substr(crime, 1, 1)))
v1
#[1] "11" "17" "9"  "26" "6"  "5"

In the OP's for loop, a vector can be initialized to store the output in each of the iterations

v1 <- character(nrow(df1))
for (i in seq_along(df1$crime)){
 if (nchar(df1$crime[i])==6){
      v1[i] <- substring(df1$crime[i],1,2)
   }  else {
      v1[i] <- substring(df1$crime[i],1,1)
    }
   }

Upvotes: 2

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