And And - 2 months ago 16
R Question

Transforming vector into matrix-like object

I have a trouble with transforming vector into matrix-like object. From the first sight, it must be very easy problem, but I didn't manage to solve it yet.

Descriptinon of the problem:

I have some long vector, which resembles the below mentioned one:

m <- c("100€", "25m²", "2 rooms", "12m²", "4 rooms", "500€", "3 rooms")


I wish to transfer it into the data.frame (or matrix) of the following structure:

price surface rooms
100€ 25m² 2 rooms
NA 12m² 4 rooms
500€ NA 3 rooms

Answer

You may try something like this, calculate the column and row index respectively and then assign the vector to the matrix using the indices:

col <- ifelse(grepl("€", m), 1, ifelse(grepl("m²", m), 2, 3))

col
# [1] 1 2 3 2 3 1 3

row <- cumsum(c(T, diff(col) < 0))     # calculate the row index based on the column index, 
                                       # when you encounter a decrease of the column index, 
                                       # increase the row index by one
row
# [1] 1 1 1 2 2 3 3

mat <- matrix(nrow = max(row), ncol = max(col))
mat[cbind(row, col)] <- m

mat
#     [,1]   [,2]   [,3]     
#[1,] "100€" "25m²" "2 rooms"
#[2,] NA     "12m²" "4 rooms"
#[3,] "500€" NA     "3 rooms"
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