[R] Reshape from long to wide
aly
I'm a total beginner in R and this question is probably very simple but I've
spent hours reading about it and can't find the answer. I'm trying to
reshape a data table from long to wide format. I've tried reshape() and
cast() but I get error messages every time and I can't figure why. In my
data, I have the length of two fish from each family. My data table (called
fish) looks like this:
family length
14 18
14 7
15 7
15 21
17 50
17 21
18 36
18 21
20 36
20 42
24 56
24 42
25 43
25 56
27 15
27 42
28 7
28 42
29 56
29 49
I want it to look like this:
family kid1 kid2
14 18 7
15 7 21
17 50 21
18 36 21
28 36 42
24 56 42
25 43 56
27 15 42
28 7 42
29 56 49
I've tried:
>cast( fish, fam~length)
and got the error message:
Using length as value column. Use the value argument to cast to override
this choice
Error in `[.data.frame`(data, , variables, drop = FALSE) :
undefined columns selected
Then I rename the columns:
>myvars<-c("fam","length")
>fish<-fish[myvars]
and try the cast() again with no luck (same error)
By using reshape() I don't get the results I want:
>reshape(rdm1, timevar="fam", idvar=c("length"), direction="wide")
> head(first)
length
14.20 14
14.19 7
15.25 21
17.30 50
18.32 36
20.36 42
Can someone help with this? Thanks a lot!
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and provide commented, minimal, self-contained, reproducible code.
Jorge I Velez
Try
# your data
x <- structure(list(family = c(14L, 14L, 15L, 15L, 17L, 17L, 18L,
18L, 20L, 20L, 24L, 24L, 25L, 25L, 27L, 27L, 28L, 28L, 29L, 29L
), length = c(18L, 7L, 7L, 21L, 50L, 21L, 36L, 21L, 36L, 42L,
56L, 42L, 43L, 56L, 15L, 42L, 7L, 42L, 56L, 49L)), .Names = c("family",
"length"), class = "data.frame", row.names = c(NA, -20L))
# processing
require(plyr)
ddply(x, .(family), function(df) c(kid1 = df$length[1], kid2 =
df$length[2]))
family kid1 kid2
1 14 18 7
2 15 7 21
3 17 50 21
4 18 36 21
5 20 36 42
6 24 56 42
7 25 43 56
8 27 15 42
9 28 7 42
10 29 56 49
HTH,
Jorge.-
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Gabor Grothendieck
Here are a few solutions. First create fish2 from fish:
fish2 <- data.frame(fish, kid = c("kid1", "kid2"))
# 1
xtabs(length ~ family + kid, DF2)
# 2
reshape(data = DF2, dir = "wide", timevar = "kid", idvar = "family")
# 3
with(fish2, data.frame(family = unique(family),
kid1 = length[kid == "kid1"],
kid2 = length[kid == "kid2"]))
# 4
library(reshape)
cast(family ~ kid, data = fish2, value = "length")
# 5
library(reshape2)
dcast(family ~ kid, data = fish2, value.var = "length")
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Tyler Rinker
Another approach, as your needs are very specific (take every other item in the second column and the unique values of columns 1) would be to index, use unique and put it together with data.frame (or cbind).
data.frame(family = unique(x[, 1]), kid1 = x[c(T, F), 2], kid2 = x[c(F, T), 2])
Cheers,Tyler
aly
Thanks a lot,
I tried one of the ways you guys showed me and it totally work. Just for
fun, I tried all the others and with some modifications here and there they
work fine too. It was time consuming but definitely worth as a good learning
experience. Thanks again
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