Myujth

I have a column in my spreadsheet called CourseType and the value in the column is either O, OS or C. I want to change the letters to read Online, Onsite.

How would I do this using R?

Thanks
Paul

Assuming the dataframe is called df and the column is named CourseType, you can use an ifelse statement if the options to be replaced are limited. This is similar to the nested IF-ELSE in excel:

df$CourseType_new <- ifelse(df$CourseType == "O", "Online", 
 ifelse(df$CourseType == "OS", "OnSite", "something else"))

If you have more values, I'd suggest using a lookup table

If you want to avoid ifelse cascades (e. g. in case of many different codes) you can use this approach:

# Construct example data
df <- data.frame(CourseType = c("C", "O", "O", "OS", "OS", "C"), teacher = c("Joe", "Jane"), stringsAsFactors = FALSE)
df
# CourseType teacher
# 1 C Joe
# 2 O Jane
# 3 O Joe
# 4 OS Jane
# 5 OS Joe
# 6 C Jane

# Do recode by filtering the lines
df$CourseType[df$CourseType == "O"] <- "Online"
df$CourseType[df$CourseType == "OS"] <- "OnSite"

df
# CourseType teacher
# 1 C Joe
# 2 Online Jane
# 3 Online Joe
# 4 OnSite Jane
# 5 OnSite Joe
# 6 C Jane

# Note: The non-matching CourseTypes are left unchanged!

One drawback is that you have no else part where you can set the non-recodes values to a default value... So a better approach would be to "enrich" your data.frame by adding the recoded value to a new column:

df$CourseTypeRecoded[df$CourseType == "O"] <- "Online"
df$CourseTypeRecoded[df$CourseType == "OS"] <- "OnSite"

df
# CourseType teacher CourseTypeRecoded
# 1 C Joe <NA>
# 2 O Jane Online
# 3 O Joe Online
# 4 OS Jane OnSite
# 5 OS Joe OnSite
# 6 C Jane <NA>

You could then set the NA values (which indicate an recode failure) to a default value, e. g.

df$CourseTypeRecoded[is.na(df$CourseTypeRecoded)] <- "(invalid code)"