function that outputs R code

Question

I have a dataframe in long format, like this one:

longData <- mtcars[1:5, 1:4]
library(reshape2)
melt(longData)

Using  as id variables
   variable value
1       mpg  21.0
2       mpg  21.0
3       mpg  22.8
4       mpg  21.4
5       mpg  18.7
6       cyl   6.0
7       cyl   6.0
8       cyl   4.0
9       cyl   6.0
10      cyl   8.0
11     disp 160.0
12     disp 160.0
13     disp 108.0
14     disp 258.0
15     disp 360.0
16       hp 110.0
17       hp 110.0
18       hp  93.0
19       hp 110.0
20       hp 175.0

Is it possible to make a function that would spit out the R code that would build the same dataframe in wide format? Note: I do not want to convert longData to wide format, I want to programatically output R code code that would convert the dataframe to wide format, like this:

someFunctionToOutputWideCode()

data.frame(mpg = c(21.0, 21.0, 22.8, 21.4, 18.7),
           cyl = c(6, 6, 4, 6, 8),
           disp = c(160, 160, 108, 258, 360),
           hp = c(110, 110, 93, 110, 175))

Why not just wrap the code which would convert the data to wide format inside dput()? — Brian Diggs
– Brian Diggs, Commented May 17, 2013 at 21:15

eddi · Accepted Answer · 2013-05-17 19:58:06Z

3

I don't think that's what people mean when they talk about long and wide formats, but how about this to achieve what you want?

dput(as.data.frame(t(longData)))
# structure(list(`Mazda RX4` = c(21, 6, 160, 110), `Mazda RX4 Wag` = c(21, 
# 6, 160, 110), `Datsun 710` = c(22.8, 4, 108, 93), `Hornet 4 Drive` = c(21.4, 
# 6, 258, 110), `Hornet Sportabout` = c(18.7, 8, 360, 175)), .Names = c("Mazda RX4", 
# "Mazda RX4 Wag", "Datsun 710", "Hornet 4 Drive", "Hornet Sportabout"
# ), row.names = c("mpg", "cyl", "disp", "hp"), class = "data.frame")

Re OP edit: same idea - convert it to whatever format you like, and then dput it

dput(dcast(melt(longData), 1:5 ~ variable))
# structure(list(`1:5` = 1:5, mpg = c(21, 21, 22.8, 21.4, 18.7), 
#     cyl = c(6, 6, 4, 6, 8), disp = c(160, 160, 108, 258, 360), 
#     hp = c(110, 110, 93, 110, 175)), .Names = c("1:5", "mpg", 
# "cyl", "disp", "hp"), row.names = c(NA, -5L), class = "data.frame")

edited May 17, 2013 at 19:58

answered May 17, 2013 at 19:29

eddi

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1 Comment

luciano Over a year ago

Apologies, just realised mtcars was already in wide format. Question amended.

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