R, list the subject(s) where a studient is "B" or "C"

Question

I am beginning with R. I am testing with a dataset called "students". Its a matrix with the name of the student and their classification (A, B, C) on several subjects (Vars). I would like to filter the name and list the subject(s) when the subject has a value "B" or "C". Please see what I have and what I would like to get.

Thank you for your help

What I have...

Name    MATH    LANG    GYMN    LIT SOC
Nigel   A   B   C   A   C
John    C   C   A   B   C
Martha  A   A   A   A   A

I wish...

Nigel   
LANG 
GYMN
SOC

John
MATH
LANG
LIT
SOC

Hi, and welcome to SO! In general it's hard to answer questions that provide screenshots of data, because we don't know how the data is actually organised in your R session. Take a look at [how to make a reproducible example in R](https://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). In this case, we don't know if your Student Matrix is actually a matrix or a dataframe, and we don't know whether you want a list, character vector or a dataframe out. — Calum You, Apr 24 '19 at 22:17

score 0 · Accepted Answer · answered Apr 24 '19 at 22:16

Using the following data,

data <- data.frame(row.names = c("Nigel", "John", "Martha"),
               MATH = c("A", "C", "A"),
               LANG = c("B", "C", "A"),
               GYMN = c("C", "A", "A"),
               LIT = c("A", "B", "A"),
               SOC = c("C", "C", "A"))

We can apply our test to each row of the data, (there are more efficient ways, but this is very instructive),

rst <- apply(data, 1, function(x) which(x == "B" | x == "C"))

$Nigel
LANG GYMN  SOC 
   2    3    5 

$John
MATH LANG  LIT  SOC 
   1    2    4    5 

$Martha
named integer(0)

This returns a list with the relevant subjects, use, for example rst$Nigel to get the relevant students information

R, list the subject(s) where a studient is "B" or "C"

1 Answers1