Transpose Rows in batches to Columns in R

Question

My data.frame df looks like this:

A 1  
A 2  
A 5  
B 2  
B 3  
B 4  
C 3  
C 7  
C 9  

I want it to look like this:

A B C  
1 2 3  
2 3 7  
5 4 9  

I have tried spread() but probably not in the right way. Any ideas?

Answer 1

We can use unstack from base R

unstack(df1, col2 ~ col1)
#  A B C
#1 1 2 3
#2 2 3 7
#3 5 4 9

Or with split

data.frame(split(df1$col2, df1$col1))

---

Or if we use spread or pivot_wider, make sure to create a sequence column

library(dplyr)
library(tidyr)
df1 %>%
  group_by(col1) %>%
  mutate(rn = row_number()) %>%
  ungroup %>%
  pivot_wider(names_from = col1, values_from = col2) %>%
  # or use
  # spread(col1, col2) %>%
  select(-rn)
# A tibble: 3 x 3
#      A     B     C
#  <int> <int> <int>
#1     1     2     3
#2     2     3     7
#3     5     4     9

---

Or using dcast

library(data.table)
dcast(setDT(df1), rowid(col1) ~ col1)[, .(A, B, C)]

data

df1 <- structure(list(col1 = c("A", "A", "A", "B", "B", "B", "C", "C", 
"C"), col2 = c(1L, 2L, 5L, 2L, 3L, 4L, 3L, 7L, 9L)),
   class = "data.frame", row.names = c(NA, 
-9L))