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Comparing dcast and reshape
3 messages · David Winsemius, Nutter, Benjamin
On Oct 17, 2012, at 2:09 PM, Nutter, Benjamin wrote:
I'm in the middle of my own little intellectual exercise comparing
dcast() and reshape() and have successfully stumped myself. I want to
melt() a data frame, then dcast() it into a new form. After doing
so, I
want to duplicate the process using reshape().
So far, I can do the melt and cast
require(reshape2)
Raw <- data.frame(site = c(1, 1, 1, 1, 2, 2, 2, 2),
id = c(1, 1, 2, 2, 1, 1, 2, 2),
instrument = rep(c("beck", "phq"), 4),
base.score = c(27, 13, 31, 11, 22, 10, 41, 17),
score.90d = c(20, 11, 27, 12, 24, 8, 34, 15))
Full.Melt <- melt(Raw, id.vars=c("site", "id", "instrument"),
measure.vars=c("base.score", "score.90d"))
FullCast <- dcast(Full.Melt, site + id ~ instrument + variable,
value.var="value")
FullCast
site id beck_base.score beck_score.90d phq_base.score phq_score.90d
1 1 1 27 20 13 11
2 1 2 31 27 11 12
3 2 1 22 24 10 8
4 2 2 41 34 17 15
I can also replicate the melt using reshape, but I can't reshape it
into
the same wide format.
FullLong <- reshape(Raw,
varying=list(score=c("base.score", "score.90d")),
idvar=c("site", "id", "instrument"),
direction="long")
Any pointers on how to get FullLong into the same wide format as
FullCast?
The reshape function will "recognize" that the object was created as a wide->long reshaping and if you just use this code, you will get back the original: reshape(FullLong)
David Winsemius, MD Alameda, CA, USA
Thanks for the prompt reply, Dr. Winsemius.
reshape(FullLong)
Will return the original data frame, but that wasn't quite what I wanted. I wanted to take it to a wider form than the original.
But I just answered my own question (typically, _after_ asking the world at large).
FullWide <- reshape(Raw,
v.names=c("base.score", "score.90d"),
timevar="instrument",
idvar=c("site", "id"),
direction="wide")
gives me what I was looking for. I suspect there isn't a way to go directly from FullLong to FullWide, but if someone can prove me wrong, I'd love to see how.
? Benjamin Nutter |??Biostatistician ? |??Quantitative Health Sciences
? Cleveland Clinic? | ?9500 Euclid Ave.? | ?Cleveland, OH 44195? |?(216) 445-1365
-----Original Message-----
From: David Winsemius [mailto:dwinsemius at comcast.net]
Sent: Wednesday, October 17, 2012 5:18 PM
To: Nutter, Benjamin
Cc: r-help at r-project.org
Subject: Re: [R] Comparing dcast and reshape
On Oct 17, 2012, at 2:09 PM, Nutter, Benjamin wrote:
I'm in the middle of my own little intellectual exercise comparing
dcast() and reshape() and have successfully stumped myself. I want to
melt() a data frame, then dcast() it into a new form. After doing so,
I want to duplicate the process using reshape().
So far, I can do the melt and cast
require(reshape2)
Raw <- data.frame(site = c(1, 1, 1, 1, 2, 2, 2, 2),
id = c(1, 1, 2, 2, 1, 1, 2, 2),
instrument = rep(c("beck", "phq"), 4),
base.score = c(27, 13, 31, 11, 22, 10, 41, 17),
score.90d = c(20, 11, 27, 12, 24, 8, 34, 15))
Full.Melt <- melt(Raw, id.vars=c("site", "id", "instrument"),
measure.vars=c("base.score", "score.90d"))
FullCast <- dcast(Full.Melt, site + id ~ instrument + variable,
value.var="value")
FullCast
site id beck_base.score beck_score.90d phq_base.score phq_score.90d
1 1 1 27 20 13 11
2 1 2 31 27 11 12
3 2 1 22 24 10 8
4 2 2 41 34 17 15
I can also replicate the melt using reshape, but I can't reshape it
into the same wide format.
FullLong <- reshape(Raw,
varying=list(score=c("base.score", "score.90d")),
idvar=c("site", "id", "instrument"),
direction="long")
Any pointers on how to get FullLong into the same wide format as
FullCast?
The reshape function will "recognize" that the object was created as a wide->long reshaping and if you just use this code, you will get back the original: reshape(FullLong)
David Winsemius, MD Alameda, CA, USA =================================== Please consider the environment before printing this e-mail Cleveland Clinic is ranked one of the top hospitals in America by U.S.News & World Report (2012). Visit us online at http://www.clevelandclinic.org for a complete listing of our services, staff and locations. Confidentiality Note: This message is intended for use ...{{dropped:18}}