Remove row with specific number in R - r

Question

I want to remove row with the test "student2". However, I don't want to remove row like "student22", "student 23"... etc.
For example:
Student.Code Values
1 canada.student12 2
2 canada.student2 3 # remove
3 canada.student23 5 # keep
4 US.student2 6 # remove
5 US.student32 2
6 Aus.student87 645
7 Turkey.student25 4 #keep
I used the code grepl("student2", example$Student.code, fixed = TRUE but it also find (remove) the rows with like "student23"

Answer 1

We can use grepl("student2$", example$Student.Code)
library(tidyverse)
example <- tibble::tribble(
~Student.Code, ~Values,
"canada.student12", 2L,
"canada.student2", 3L,
"canada.student23", 5L,
"US.student2", 6L,
"US.student32", 2L,
"Aus.student87", 645L,
"Turkey.student25", 4L
)
example$Student.Code
grepl("student2$", example$Student.Code)
[1] FALSE TRUE FALSE TRUE FALSE FALSE FALSE
example %>%
filter(!grepl("student2$", Student.Code))
# A tibble: 5 x 2
Student.Code Values
<chr> <int>
1 canada.student12 2
2 canada.student23 5
3 US.student32 2
4 Aus.student87 645
5 Turkey.student25 4

Answer 2

Data:
df <- data.frame(
Student = c("canada.student12", "canada.student2", "canada.student23","US.student2", "US.student32", "Aus.student87", "Turkey.student25"),
Value = c(2,3,5,6,2,654,5)
)
Solution: (in base R)
The idea is to use grepl to match those values where the number 2 occurs at the word boundary, that is, in regex, at \\b, and to exclude these strings with the negator !:
df[!grepl("student2\\b", df$Student),]
Student Value
1 canada.student12 2
3 canada.student23 5
5 US.student32 2
6 Aus.student87 654
7 Turkey.student25 5
Alternatively, you can also go the opposite way and match those patterns that you want to keep:
df[grepl("student(?=\\d{2,})", df$Student, perl = T),]
Here, the idea is to use positive lookahead to match values with student iff they are followed immediately by at least two digits (\\d{2,}). (Note that when using lookahead or lookbehind you need to include perl = T.)

Answer 3

If you have a variable with an exact value you want to remove, don't use grep or grepl.
example <- tibble::tribble(
~Student.Code, ~Values,
"canada.student12", 2L,
"canada.student2", 3L,
"canada.student23", 5L,
"US.student2", 6L,
"US.student32", 2L,
"Aus.student87", 645L,
"Turkey.student25", 4L
)
example <- example[example$Student.Code != "canada.student2",]
# or, in dplyr
example <- filter(example, Student.Code != "canada.student2")
# for multiple values
example <- filter(example, !(Student.Code %in% c("canada.student2", "US.student2")))
fixed = TRUE is not working because all it means is 'search for this exact string in the input strings', not 'only match this exact string (it must be the whole value)'