By Matthew Leitao

2018-07-12 00:15:05 8 Comments

My question is in attempting to create a new variable based on existing variables.

I have a data set on bunch of different types of classes and class numbers, and whether or not the class was online or offline.

What I am having trouble with is figuring out how to write code to check if there is multiple of the same class that are also different types (i.e. offline or online).

So presumable it would check like this

1. Test Class ,  1, Online
2. Test Class ,  2, Offline
3. Basic Class,  1, Online
4. Test Class ,  3, Offline
5. Basic Class,  2, Offline
6. Test Class ,  1, Offline

so it would report back when two classes match on Class name, class number, and if there is both an online and offline section. Like this

True, False, False, False, False, True

That way I can sort based on the new variable created and compare only similar classes of different section types.


@G. Grothendieck 2018-07-12 00:26:12

Using DF from the Note at the end this uses only base R

differ <- function(x) length(x) == 2 && x[1] != x[2]
transform(DF, V4 = ave(as.character(V3), V1, V2, FUN = differ))


           V1 V2      V3    V4
1  Test Class  1  Online  TRUE
2  Test Class  2 Offline FALSE
3 Basic Class  1  Online FALSE
4  Test Class  3 Offline FALSE
5 Basic Class  2 Offline FALSE
6  Test Class  1 Offline  TRUE


Lines <- "
Test Class ,  1, Online
Test Class ,  2, Offline
Basic Class,  1, Online
Test Class ,  3, Offline
Basic Class,  2, Offline
Test Class ,  1, Offline"

DF <- read.table(text = Lines, sep = ",", strip.white = TRUE)

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