Hi all,
I have a data.frame with the following colnames pattern:
x1 y11 x2 y21 y22 y23 x3 y31 y32 ...
I.e. I have an x followed by a few y's. What I would like to do is turn
this wide format into a tall format with two columns: "x",
"y". The
structure is that xi needs to be associated with yij (e.g. x1 should
next to y11 and y12, x2 should be next to y21, y22, and y23, etc.).
x y
x1 y11
x2 y21
x2 y22
x2 y23
x3 y31
x3 y32
...
I have looked at ?reshape but I didn't see how it could work with this
structure. I have a solution using nested for loops (see below), but
it's slow and not very efficient. I would like to find a vectorised
solution that would achieve the same thing.
Now, for an example:
x <- data.frame(x1 = 1: 5, y11 = 1: 5,
x2 = 6:10, y21 = 6:10, y22 = 11:15,
x3 = 11:15, y31 = 16:20,
x4 = 16:20, y41 = 21:25, y42 = 26:30, y43 = 31:35)
# which are the x columns
nmx <- grep("^x", names(x))
# which are the y columns
nmy <- grep("^y", names(x))
# grab y values
y <- unlist(x[nmy])
# reserve some space for the x's
z <- vector("numeric", length(y))
# a loop counter
k <- 0
n <- nrow(x)
seq.n <- seq(n)
# determine how many times to repeat the x's
repy <- diff(c(nmx, length(names(x)) + 1)) - 1
for(i in seq(along = nmx)) {
for(j in seq(repy[i])) {
# store the x values in the appropriate z indices
z[seq.n + k * n] <- x[, nmx[i]]
# move to next block in z
k <- k + 1
}
}
data.frame(x = z, y = y, row.names = NULL)
Sundar: As I understand it, you can easily create an index variable (a pointer, actually) that will pick out the y columns in order: z<-yourdataframe y<-as.vector(z[,indexvar]) So if you could cbind() the x's, you'd be all set. Again, assuming I understand correctly, the x column you want is: x<-z[,-indexvar] ## still a frame/matrix nvec<-seq(length=ncol(x)) x<-as.vector(x[,rep(nvec,times=nvec)]) HTH -- and even if I got it wrong, it was fun, so thanks. -- Bert -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box> -----Original Message----- > From: r-help-bounces at stat.math.ethz.ch > [mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Sundar > Dorai-Raj > Sent: Tuesday, September 14, 2004 9:16 AM > To: R-help > Subject: [R] reshaping some data > > Hi all, > I have a data.frame with the following colnames pattern: > > x1 y11 x2 y21 y22 y23 x3 y31 y32 ... > > I.e. I have an x followed by a few y's. What I would like to > do is turn > this wide format into a tall format with two columns: "x", "y". The > structure is that xi needs to be associated with yij (e.g. x1 should > next to y11 and y12, x2 should be next to y21, y22, and y23, etc.). > > x y > x1 y11 > x2 y21 > x2 y22 > x2 y23 > x3 y31 > x3 y32 > ... > > I have looked at ?reshape but I didn't see how it could work > with this > structure. I have a solution using nested for loops (see below), but > it's slow and not very efficient. I would like to find a vectorised > solution that would achieve the same thing. > > Now, for an example: > > x <- data.frame(x1 = 1: 5, y11 = 1: 5, > x2 = 6:10, y21 = 6:10, y22 = 11:15, > x3 = 11:15, y31 = 16:20, > x4 = 16:20, y41 = 21:25, y42 = 26:30, y43 = 31:35) > # which are the x columns > nmx <- grep("^x", names(x)) > # which are the y columns > nmy <- grep("^y", names(x)) > # grab y values > y <- unlist(x[nmy]) > # reserve some space for the x's > z <- vector("numeric", length(y)) > # a loop counter > k <- 0 > n <- nrow(x) > seq.n <- seq(n) > # determine how many times to repeat the x's > repy <- diff(c(nmx, length(names(x)) + 1)) - 1 > for(i in seq(along = nmx)) { > for(j in seq(repy[i])) { > # store the x values in the appropriate z indices > z[seq.n + k * n] <- x[, nmx[i]] > # move to next block in z > k <- k + 1 > } > } > data.frame(x = z, y = y, row.names = NULL) > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >
Try:
x <- data.frame(x1 = 1: 5, y11 = 1: 5,
x2 = 6:10, y21 = 6:10, y22 = 11:15,
x3 = 11:15, y31 = 16:20,
x4 = 16:20, y41 = 21:25, y42 = 26:30, y43 = 31:35)
df.names<-names(x)
ynames<-df.names[grep("y",df.names)]
xnames<-substring(sub("y","x",ynames),1,2)
cbind(unlist(x[,xnames]),unlist(x[,ynames]))
Peter
Sundar Dorai-Raj wrote:
> Hi all,
> I have a data.frame with the following colnames pattern:
>
> x1 y11 x2 y21 y22 y23 x3 y31 y32 ...
>
> I.e. I have an x followed by a few y's. What I would like to do is
> turn this wide format into a tall format with two columns: "x",
"y".
> The structure is that xi needs to be associated with yij (e.g. x1
> should next to y11 and y12, x2 should be next to y21, y22, and y23,
> etc.).
>
> x y
> x1 y11
> x2 y21
> x2 y22
> x2 y23
> x3 y31
> x3 y32
> ...
>
> I have looked at ?reshape but I didn't see how it could work with this
> structure. I have a solution using nested for loops (see below), but
> it's slow and not very efficient. I would like to find a vectorised
> solution that would achieve the same thing.
>
> Now, for an example:
>
> x <- data.frame(x1 = 1: 5, y11 = 1: 5,
> x2 = 6:10, y21 = 6:10, y22 = 11:15,
> x3 = 11:15, y31 = 16:20,
> x4 = 16:20, y41 = 21:25, y42 = 26:30, y43 = 31:35)
> # which are the x columns
> nmx <- grep("^x", names(x))
> # which are the y columns
> nmy <- grep("^y", names(x))
> # grab y values
> y <- unlist(x[nmy])
> # reserve some space for the x's
> z <- vector("numeric", length(y))
> # a loop counter
> k <- 0
> n <- nrow(x)
> seq.n <- seq(n)
> # determine how many times to repeat the x's
> repy <- diff(c(nmx, length(names(x)) + 1)) - 1
> for(i in seq(along = nmx)) {
> for(j in seq(repy[i])) {
> # store the x values in the appropriate z indices
> z[seq.n + k * n] <- x[, nmx[i]]
> # move to next block in z
> k <- k + 1
> }
> }
> data.frame(x = z, y = y, row.names = NULL)
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
Try this:
is.x <- substr(colnames(x),1,1) == "x" # TRUE if col name starts
with x
x. <- unlist(rep(x[,is.x], diff(which(c(is.x,TRUE)))-1)) # repeat x cols
names(x.) <- NULL
y. <- unlist(x[,!is.x])
DF <- data.frame(x = x., y = y., row.names = NULL)
Sundar Dorai-Raj <sundar.dorai-raj <at> PDF.COM> writes:
:
: Hi all,
: I have a data.frame with the following colnames pattern:
:
: x1 y11 x2 y21 y22 y23 x3 y31 y32 ...
:
: I.e. I have an x followed by a few y's. What I would like to do is turn
: this wide format into a tall format with two columns: "x",
"y". The
: structure is that xi needs to be associated with yij (e.g. x1 should
: next to y11 and y12, x2 should be next to y21, y22, and y23, etc.).
:
: x y
: x1 y11
: x2 y21
: x2 y22
: x2 y23
: x3 y31
: x3 y32
: ...
:
: I have looked at ?reshape but I didn't see how it could work with this
: structure. I have a solution using nested for loops (see below), but
: it's slow and not very efficient. I would like to find a vectorised
: solution that would achieve the same thing.
:
: Now, for an example:
:
: x <- data.frame(x1 = 1: 5, y11 = 1: 5,
: x2 = 6:10, y21 = 6:10, y22 = 11:15,
: x3 = 11:15, y31 = 16:20,
: x4 = 16:20, y41 = 21:25, y42 = 26:30, y43 = 31:35)
: # which are the x columns
: nmx <- grep("^x", names(x))
: # which are the y columns
: nmy <- grep("^y", names(x))
: # grab y values
: y <- unlist(x[nmy])
: # reserve some space for the x's
: z <- vector("numeric", length(y))
: # a loop counter
: k <- 0
: n <- nrow(x)
: seq.n <- seq(n)
: # determine how many times to repeat the x's
: repy <- diff(c(nmx, length(names(x)) + 1)) - 1
: for(i in seq(along = nmx)) {
: for(j in seq(repy[i])) {
: # store the x values in the appropriate z indices
: z[seq.n + k * n] <- x[, nmx[i]]
: # move to next block in z
: k <- k + 1
: }
: }
: data.frame(x = z, y = y, row.names = NULL)