CODEWITHSUNDEEP
r
jmo
jmo

Reputation: 113

Create logical vector from table in R

I'm looking at the data set pre-loaded into R called UCBAdmissions:

> str(UCBAdmissions)
table [1:2, 1:2, 1:6] 512 313 89 19 353 207 17 8 120 205 ...
- attr(*, "dimnames")=List of 3
..$ Admit : chr [1:2] "Admitted" "Rejected"
..$ Gender: chr [1:2] "Male" "Female"
..$ Dept  : chr [1:6] "A" "B" "C" "D" ...

I'd like to create a logical vector of every female where TRUE equates to "Admitted" and FALSE to "Rejected." How do I do that?

Second somewhat related question -- if I wanted to make matrix out of a vector, what would the notation for that be? For lists and data.frame I can use data$variable.I.wish.to.extract.

Jen

Upvotes: 0

Views: 2169

Answers (2)

Grace Mahoney
Grace Mahoney

Reputation: 505

If the "with" command isn't working for you, you can also try the following to create your logical vector:

logical.vector <- ifelse(UCBAdmissions$Gender == "Female" & UCBAdmissions$Admit == "Admitted", TRUE, FALSE)

However, this logical vector includes males, meaning that you will get a false for all males in addition to females who were not admitted.

If you want a logical vector that truly returns FALSE only when it is a female who was not admitted, and TRUE when it is a female was was admitted, you will have to first subset the data like so:

females <- subset(UCBAdmissions, Gender == FEMALE)
logical.vector <- ifelse(females$Admit == "Admitted", TRUE, FALSE)

Hope this helps clarify a bit!

Upvotes: 1

Gavin Simpson
Gavin Simpson

Reputation: 174788

This is incomplete but was too long to add as a comment. I will delete this or update it should the OP clarify what they want to achieve

For the first question, convert the UCBAdmissions object, which is a "table" object to a data frame, and then create a logical:

UCB <- as.data.frame(UCBAdmissions)
ind <- with(UCB, Gender == "Female" & Admit == "Admitted")

which gives

R> ind
 [1] FALSE FALSE  TRUE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE  TRUE FALSE
[13] FALSE FALSE  TRUE FALSE FALSE FALSE  TRUE FALSE FALSE FALSE  TRUE FALSE

I suspect this *isn't what you want though, as the data are stored in contingency table format; there are only aggregated counts in the various classes. What ind is indexing is which rows of UCB where Gender == "Female" and Admit = "Admitted". You'd get the same number of TRUE and FALSE values if you asked for Gender == "Female" and Admit = "Rejected", just in a different order.

If you want to blow that out to actual data, you need to repeat the rows of UCB

R> head(UCB)
     Admit Gender Dept Freq
1 Admitted   Male    A  512
2 Rejected   Male    A  313
3 Admitted Female    A   89
4 Rejected Female    A   19
5 Admitted   Male    B  353
6 Rejected   Male    B  207

Freq times for each row, and then create the logical vector. Is that what you want?

Upvotes: 1

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