Create multiple csv files based on transpose

问题

I have a dataframe that looks like below:

CustID  item    sales
1       a1      40
1       a2      40
1       a3      34
1       a4      42
1       a5      21
1       a6      22
2       a1      33
2       a2      30
2       a3      21
2       a4      11
2       a5      19
2       a6      20

I need to create 2 transposed data sets (they should be CSVs) such that each one contains item in groups of 3 each.....

OUTPUT:

csv1 (item 1-3)         
CustID  itema1  itema2  itema3
1         40      40     34
2         33      30     21

csv2 (item 4-6)         
CustID  itema4  itema5  itema6
1         42     21      22
2         11     19      20

Please help me out here

回答1:

Not an one-liner solution, but it does what you want.

First using a combination of split and dcast you can create and transpose the df.

> items <- split(df, df$item)
> 
> library(reshape2)
> dcast(do.call(rbind, items[1:3]), CustID~item )
  CustID a1 a2 a3
1      1 40 40 34
2      2 33 30 21

> dcast(do.call(rbind, items[4:6]), CustID~item )
  CustID a4 a5 a6
1      1 42 21 22
2      2 11 19 20

Then using write.csv you can create and save the data.frames into a csv file.

Here's all in one shot:

lapply(seq(1, length(items), 3), function(i){
  DF <- dcast(do.call(rbind, items[i:(i+2)]), CustID~item )
  write.csv(DF, file = paste0("DF", i, ".csv"))
})

回答2:

Here is another approach, using xtabs from base R:

x <- xtabs(sales ~ CustID + item, mydf)
x
#       item
# CustID a1 a2 a3 a4 a5 a6
#      1 40 40 34 42 21 22
#      2 33 30 21 11 19 20

^^ That first step transposes the data for you.

fileout <- list(A = 1:3, B = 4:6)

Here, we have created a named list of the columns you want to export for each CSV. The names of the list items would be used for the CSV filenames.

Below is an example of how you can use lapply to write your CSV files.

lapply(seq_along(fileout), function(y) 
  write.csv(x[, fileout[[y]]], 
            file = paste(names(fileout[y]), ".csv", sep = "")))

来源：https://stackoverflow.com/questions/19155457/create-multiple-csv-files-based-on-transpose

标签

transpose