Convert list of matrices into a single summary data frame

June 9, 2023

I have a list of matrices.

# Sample data
m1 <- matrix(c(5, 2, 8, 3, 10, 3), nrow = 2, ncol = 3, dimnames = list(c("Mean", "SD"), c("Apples", "Oranges", "Bananas")))
m2 <- matrix(c(4, 1, 7, 2, 9, 2), nrow = 2, ncol = 3, dimnames = list(c("Mean", "SD"), c("Apples", "Oranges", "Bananas")))
m3 <- matrix(c(6, 3, 9, 4, 11, 4), nrow = 2, ncol = 3, dimnames = list(c("Mean", "SD"), c("Apples", "Oranges", "Bananas")))

# Create a list of data frames
matrix_list <- list(m1 = m1, m2 = m2, m3 = m3)

I want to combine the matrices in the list to make a summary data frame with the following structure.

    Apples_Mean Apples_SD Oranges_Mean Oranges_SD Bananas_Mean Bananas_SD
m1            5         2            8          3           10          3
m2            4         1            7          2            9          2
m3            6         3            9          4           11          4

How can I do this?

>Solution :

With base R, you can use xtabs + Map + as.data.frame like below

xtabs(
    Freq ~ m + paste0(Var2, "_", Var1),
    do.call(
        rbind,
        Map(
            \(x, y) cbind(
                m = x,
                as.data.frame(as.table(y))
            ),
            names(matrix_list),
            matrix_list
        )
    )
)

which gives

    paste0(Var2, "_", Var1)
m    Apples_Mean Apples_SD Bananas_Mean Bananas_SD Oranges_Mean Oranges_SD
  m1           5         2           10          3            8          3
  m2           4         1            9          2            7          2
  m3           6         3           11          4            9          4