Creating a string variable based on another variable

[dtlbyrd]

Hello all,

I have a simple question, but I can't find the correct code to do it. I tried grepl, but that didn't work. I want to create a value (string) for a new variable based on another variable containing a specific word.

If Var1 contains "apples" then var2="fruit"

Sample dataset
Var1 Var 2
apples Fruit
cats NA
green apples Fruit

Thanks!

Dan

[andresrcs]

df <- data.frame(stringsAsFactors = FALSE,
                 Var1 = c("apples", "cats", "green apples"))
df$Var2 <- ifelse(grepl("apples", df$Var1), "Fruit", NA)
df
#>           Var1  Var2
#> 1       apples Fruit
#> 2         cats  <NA>
#> 3 green apples Fruit

^{Created on 2019-03-28 by the reprex package (v0.2.1)}

[dtlbyrd]

Thank you for all of your help!

Dan

[dtlbyrd]

Quick follow up. What if you have multiple clauses? it seems the "NA" aspect overrides all other clauses

Var 1	Var 2
apples	fruit
cats	animal
green cats	animal
green apples	fruit
red cats	animal

In this case

If it contains apples, its fruit if it contains cats it’s an animal.

Thanks

[Yarnabrina]

What about this?

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union

df <- data.frame(stringsAsFactors = FALSE,
                 Var1 = c("apples", "cats", "green cats", "green apples", "red cats"))

df %>%
  mutate(Var2 = case_when(grepl("apples", Var1) ~ "fruit",
                          grepl("cats", Var1) ~ "animal"))
#>           Var1   Var2
#> 1       apples  fruit
#> 2         cats animal
#> 3   green cats animal
#> 4 green apples  fruit
#> 5     red cats animal

^{Created on 2019-03-29 by the reprex package (v0.2.1)}

You can also use if - else if - else

[dtlbyrd]

Got it! thanks again for your help!

Dan

[dtlbyrd]

df %>%

Your code works perfectly, but I can't translate it. I'm new to R

df$Var2="NA"
mutate(df$var2 = case_when(grepl("apples", df$var1) ~ "fruit",
grepl("cats", df$var1) ~ "animal"))

Error: unexpected '=' in "mutate(df$var2 ="

Error: unexpected ')' in " grepl("cats", df$var1) ~ "animals")"

[andresrcs]

If you don't want to use the pipe operator %>% then you have to specify the .data parameter for mutate() and you shouldn't use df$Var1 when working with dplyr just use Var1

mutate(.data = df, Var2 = case_when(grepl("apples", Var1) ~ "fruit",
                                    grepl("cats", Var1) ~ "animal"))
#>           Var1   Var2
#> 1       apples  fruit
#> 2         cats animal
#> 3   green cats animal
#> 4 green apples  fruit
#> 5     red cats animal

If you want to learn how to use dplyr an the rest of the tidyverse tools you can read this free online book.

1 Introduction | R for Data Science

[dtlbyrd]

mutate(.data = df, Var2 = case_when(grepl("apples", Var1) ~ "fruit", grepl("cats", Var1) ~ "animal"))

Thanks again for your help!

Dan