CODEWITHSUNDEEP
r
user2716568
user2716568

Reputation: 1946

How to use chained ifelse and grepl?

I have a database of thoroughbred names that is structured as follows:

HorseName <- c("Grey emperor", "Smokey grey", "Gaining greys", "chestnut", "Glowing Chestnuts", "Ruby red", "My fair lady", "Man of war")
Number <- seq(1:8)
df <- data.frame(HorseName, Number)

I now wish to search for occurences of colours within each horse's name. Specifically, I wish to select all the instances of 'grey' and 'chestnut', creating a new column that identifies these colours. Any other names can be simply 'other' Unfortunately, the names are not consistent, with plurals included and varying case formats. How would I go about doing this in R?

My anticipated output would be:

df$Type <- c("Grey", "Grey", "Grey", "Chestnut", "Chestnut", "Other", "Other", "Other")

I am familiar with chained ifelse statements but unsure how to handle the plural occurences and case sensitivities!

Upvotes: 1

Views: 510

Answers (2)

markdly
markdly

Reputation: 4534

In case you are interested in other ways to do this, here's a tidyverse alternative which has the same end result as @amrrs answer. 

library(tidyverse)
library(stringr)

df %>% 
  mutate(Type = str_extract(str_to_lower(HorseName), "grey|chestnut")) %>%
  mutate(Type = str_to_title(if_else(is.na(Type), "other", Type)))
#>           HorseName Number     Type
#> 1      Grey emperor      1     Grey
#> 2       Smokey grey      2     Grey
#> 3     Gaining greys      3     Grey
#> 4          chestnut      4 Chestnut
#> 5 Glowing Chestnuts      5 Chestnut
#> 6          Ruby red      6    Other
#> 7      My fair lady      7    Other
#> 8        Man of war      8    Other

Upvotes: 3

amrrs
amrrs

Reputation: 6325

Converting all the input text df$HorseName to lower case before pattern matching with grepl (using lower-cased pattern) solves this problem.

> df$Type <- ifelse(grepl('grey',tolower(df$HorseName)),'Grey',
+                   ifelse(grepl('chestnut',tolower(df$HorseName)),'Chestnut',
+                                'others'))
> df
          HorseName Number     Type
1      Grey emperor      1     Grey
2       Smokey grey      2     Grey
3     Gaining greys      3     Grey
4          chestnut      4 Chestnut
5 Glowing Chestnuts      5 Chestnut
6          Ruby red      6   others
7      My fair lady      7   others
8        Man of war      8   others
>

Upvotes: 2

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