I'm stumped. I have a dataset I want to melt to create a temporal sequence of
events for each subject, but in each row, I would like to retain the baseline
characteristics.
D <- structure(list(ID = c("A", "B", "C", "D", "E", "F", "G", "H", "I", "J"),
AGE = structure(c(68L, 63L, 55L, 64L, 60L, 78L, 60L, 62L,
60L, 75L),
label = "Age", class = "labelled"),
BMI = structure(c(25L, 27L, 27L, 28L, 32L, NA, 36L, 27L,
31L, 25L),
label = "BMI (kg/m2)", class = "labelled"),
EventDays = structure(c(722L, 738L, 707L, 751L, 735L, 728L,
731L, 717L, 728L, 735L),
label = "Time to first ACM/censor
(days)", class = "labelled"),
ImplantDays = c(NA, NA, 575, NA, NA, NA, 490, 643, NA,
NA)),
.Names = c("ID", "AGE", "BMI", "EventDays", "InterventionDays"),
row.names = c(NA, 10L),
class = "data.frame")
melt(D, c("ID", "AGE", "BMI")) # produces the following error
Error in data.frame(ids, variable, value, stringsAsFactors = FALSE) :
arguments imply differing number of rows: 10, 20
Now, I know AGE and BMI aren't exactly identifying variables, but my hope would
be that, since ID uniquely identifies the subjects, I could use this as a short
cut to getting the data set I want. I can get the data I want if I go about it
a little differently.
#* What I would like it to look like.
Timeline <- melt(D[, c("ID", "EventDays", "InterventionDays")], "ID",
na.rm=TRUE)
Timeline <- arrange(Timeline, ID, value)
Timeline <- merge(D[, c("ID", "AGE", "BMI")],
Timeline,
by="ID", all.x=TRUE)
At first I thought it might be the mixture of character and numeric variables
as IDs, but the following example works
A <- data.frame(id = LETTERS[1:10],
age = c(50, NA, 51, 52, 53, 54, 55, 56, 57, 58),
meas1 = rnorm(10),
meas2 = rnorm(10, 5),
stringsAsFactors=FALSE)
melt(A, c("id", "age"))
I'm sure I'm missing something really obvious (kind of like how I can stare at
the dry goods aisle for 10 minutes and still not find the chocolate chips). If
anyone could help me understand why this error is occurring, I'd greatly
appreciate it.
> sessionInfo()
R version 2.15.2 (2012-10-26)
Platform: x86_64-unknown-linux-gnu (64-bit)
locale:
[1] C
attached base packages:
[1] splines stats graphics grDevices utils datasets methods base
other attached packages:
[1] lazyWeave_2.2.3 Hmisc_3.10-1 survival_2.36-14 plyr_1.7.1
reshape2_1.2.2
loaded via a namespace (and not attached):
[1] cluster_1.14.3 grid_2.15.2 lattice_0.20-10 stringr_0.6.1 tools_2.15.2
Benjamin Nutter | Biostatistician | Quantitative Health Sciences
Cleveland Clinic | 9500 Euclid Ave. | Cleveland, OH 44195 | (216)
445-1365
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