What happened to my matrix col, it shows NA-CodePudding

I am learning R now and I want to make a matrix to store scores. I don't know why the named_matrix can't show the Student_6. The picture as below shows the Student_NA.

scores <- c(58, 46, 50, 90, 42, 52, 62, 44, 96, 92, 54, 82)

scores_matrix <- matrix(scores, nrow = 2,ncol = length(scores)/2, byrow = TRUE)
scores_matrix

named_matrix <- scores_matrix
suffix <- seq(1:n)
rownames(named_matrix) <- paste("Quiz_",suffix[1:nrow(named_matrix)],seq=" ")
colnames(named_matrix)<- paste("Student_",suffix[1:ncol(named_matrix)],seq=" ")
named_matrix

CodePudding user response：

n is undefined in your code. Also 1:n makes seq redundant.

Correcting your code -

scores <- c(58, 46, 50, 90, 42, 52, 62, 44, 96, 92, 54, 82)

scores_matrix <- matrix(scores, nrow = 2,ncol = length(scores)/2, byrow = TRUE)
scores_matrix

named_matrix <- scores_matrix
suffix <- 1:length(scores)
rownames(named_matrix) <- paste("Quiz_",suffix[1:nrow(named_matrix)],seq=" ")
colnames(named_matrix)<- paste("Student_",suffix[1:ncol(named_matrix)],seq=" ")
named_matrix

#            Student_ 1   Student_ 2   Student_ 3   Student_ 4   Student_ 5   Student_ 6  
#Quiz_ 1             58           46           50           90           42           52
#Quiz_ 2             62           44           96           92           54           82

However, you can also simplify this process.

scores <- c(58, 46, 50, 90, 42, 52, 62, 44, 96, 92, 54, 82)
n <- 2
m <- length(scores)/2
scores_matrix <- matrix(scores, nrow = n,ncol = m,byrow = TRUE, 
                      dimnames = list(paste0('Quiz_', seq_len(n)), 
                                      paste0('Student', seq_len(m))))
scores_matrix

#       Student1 Student2 Student3 Student4 Student5 Student6
#Quiz_1       58       46       50       90       42       52
#Quiz_2       62       44       96       92       54       82

CodePudding user response：

Solution

Here I just used your code up to this point:

scores <- c(58, 46, 50, 90, 42, 52, 62, 44, 96, 92, 54, 82)

scores_matrix <- matrix(scores, 
                        nrow = 2,
                        ncol = length(scores)/2, 
                        byrow = TRUE)
scores_matrix

Then just entered the names like so:

colnames(scores_matrix) <- paste("Student", 1:6)
rownames(scores_matrix) <- c("Quiz 1", "Quiz 2")
scores_matrix

Which gives you this:

       Student 1   Student 2   Student 3   Student 4   Student 5   Student 6  
Quiz 1          58          46          50          90          42          52
Quiz 2          62          44          96          92          54          82

Alternative transpose format

Also if you prefer a column format, since it is in a matrix, you can simply make a transpose of the matrix like so:

t(scores_matrix)

Which creates this:

            Quiz 1 Quiz 2
Student 1       58     62
Student 2       46     44
Student 3       50     96
Student 4       90     92
Student 5       42     54
Student 6       52     82