How to add a value inside a string

How can I add a value inside a string when a condition is met.

For example, take the following data:

my_data <- c("ab 93 1455 1863 2713 sb 673 771 1601 1969", 
             "ab 93 1098 1455 2423 2427 sb 168 673 1256", 
             "ab 93 1098; sb 1256")

I want to add a ";" when a number proceeds a character.

Therefore, I would like the output to be:

output<- c("ab 93 1455 1863 2713; sb 673 771 1601 1969", 
           "ab 93 1098 1455 2423 2427; sb 168 673 1256", 
           "ab 93 1098; sb 1256")

If this solution could be completed in the context of a data frame that would be great.

So far, I have been able to detect the condition I’m interested in using the following code:

str_detect(my_data, "[0-9] [a-z]")
[1]  TRUE  TRUE FALSE

But I am having trouble moving beyond this point.

Thank you for the help!

>Solution :

Of course, use regular expressions:

output <- gsub("(\\d)( +[a-zA-Z])", "\\1;\\2", my_data)

print(output)

# [1] "ab 93 1455 1863 2713; sb 673 771 1601 1969" "ab 93 1098 1455 2423 2427; sb 168 673 1256"
# [3] "ab 93 1098; sb 1256"