Turning off Case Sensitivity in R
I Am Having Difficulty with Case Sensitivity. Can We Turn It off? A1
I am having difficulty with case sensitivity. Can we turn it off?
A1 <- c("a", "A", "a", "a", "A", "A", "a")
B1 <- c(rep("a", length(A1)))
A1 == B1
# [1] TRUE FALSE TRUE TRUE FALSE FALSE TRUE
should be all TRUE
2 Answers
There's no way to turn off case sensitivity of ==, but coercing both character vectors to uppercase and then testing for equality amounts to the same thing:
toupper(A1)
[1] "A" "A" "A" "A" "A" "A" "A"
toupper(A1)==toupper(B1)
# [1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE
As Josh O'Brien said. To extend a bit on caseless matching in R, that is actually possible with regular expressions (using eg grep and grepl)
In this case you could use mapply and grepl like this, provided you're matching single characters :
A1 <- c("a", "A", "a", "a", "A", "A", "a")
B1 <- c(rep("a", length(A1)))
mapply(grepl,A1,B1,ignore.case=TRUE)
# a A a a A A a
# TRUE TRUE TRUE TRUE TRUE TRUE TRUE
You have to be careful though, because it also matches partial strings like this :
C1 <- rep('ab',length(A1))
mapply(grepl,A1,C1,ignore.case=TRUE)
# a A a a A A a
# TRUE TRUE TRUE TRUE TRUE TRUE TRUE
This may or may not be what you want.
On a sidenote, if you match with regular expressions and you want to ignore the case, you can also use the construct (?i) to turn on caseless matching and (?-i) to turn off caseless matching :
D1 <- c('abc','aBc','Abc','ABc','aBC')
grepl('a(?i)bc',D1) # caseless matching on B and C
# [1] TRUE TRUE FALSE FALSE TRUE
grepl('a(?i)b(?-i)c',D1) # caseless matching only on B
# [1] TRUE TRUE FALSE FALSE FALSE
Elena Rostova holds a Master's degree in Public Health Journalism. She covers groundbreaking medical research, holistic wellness trends, mental health awareness, and nutritional science.
