在R中的数据框中向下移动列

Question

Suppose I have the next data frame:

df<-data.frame(step1=c(1,2,3,4),step2=c(5,6,7,8),step3=c(9,10,11,12),step4=c(13,14,15,16))

  step1 step2 step3 step4
1     1     5     9    13
2     2     6    10    14
3     3     7    11    15
4     4     8    12    16

and what I have to do is something like the following:

df2<-data.frame(col1=c(1,2,3,4,5,6,7,8,9,10,11,12),col2=c(5,6,7,8,9,10,11,12,13,14,15,16))

   col1 col2
1     1    5
2     2    6
3     3    7
4     4    8
5     5    9
6     6   10
7     7   11
8     8   12
9     9   13
10   10   14
11   11   15
12   12   16

How can I do that? consider that more steps can be included (example, 20 steps).

Thanks!!

Answer 1

We can design a function to achieve this task. df_final is the final output. Notice that bin is an argument that the users can specify how many columns to transform together.

# A function to conduct data transformation
trans_fun <- function(df, bin = 3){
  # Calculate the number of new columns
  new_ncol <- (ncol(df) - bin) + 1
  # Create a list to store all data frames
  df_list <- lapply(1:new_ncol, function(num){
    return(df[, num:(num + bin - 1)])
  })
  # Convert each data frame to a vector
  dt_list2 <- lapply(df_list, unlist)
  # Convert dt_list2 to data frame
  df_final <- as.data.frame(dt_list2)
  # Set the column and row names of df_final
  colnames(df_final) <- paste0("col", 1:new_ncol)
  rownames(df_final) <- 1:nrow(df_final)
  return(df_final)
}

# Apply the trans_fun
df_final <- trans_fun(df)

df_final
   col1 col2
1     1    5
2     2    6
3     3    7
4     4    8
5     5    9
6     6   10
7     7   11
8     8   12
9     9   13
10   10   14
11   11   15
12   12   16

Answer 2

This should do the work:

df2 <- data.frame(col1 = 1:(length(df$step1) + length(df$step2))) df2$col1 <- c(df$step1, df$step2, df$step3) df2$col2 <- c(df$step2, df$step3, df$step4)

Things to point:

• The important thing to see in the first line of the code, is the need for creating a table with the right amount of rows
• Calling a columns that does not exist will create one, with that name
• Deleting columns in R should be done like this df2$col <- NULL

Answer 3

Here is a method using dplyr and reshape2 - this assumes all of the columns are the same length.

library(dplyr)
library(reshape2)

Drop the last column from the dataframe

df[,1:ncol(df)-1]%>% 
    melt() %>% 
    dplyr::select(col1=value) -> col1

Drop the first column from the dataframe

df %>%
    dplyr::select(-step1) %>% 
    melt() %>% 
    dplyr::select(col2=value)  -> col2

Combine the dataframes

bind_cols(col1, col2)

Answer 4

Are you not just looking to do:

df2 <- data.frame(col1 = unlist(df[,-nrow(df)]), 
                  col2 = unlist(df[,-1]))
rownames(df2) <- NULL
df2

  col1 col2 1 1 5 2 2 6 3 3 7 4 4 8 5 5 9 6 6 10 7 7 11 8 8 12 9 9 13 10 10 14 11 11 15 12 12 16