Changing dcast to show multiple columns - r

Question

I have the following situation. Consider the following df:
mymatrix <- as.data.frame(matrix(data = 0, nrow = 7, ncol = 4))
colnames(mymatrix) <- c("Patient", "marker", "Number", "Visit")
mymatrix[,1] <- c("B1","B1","C1","C1","D1","D1","D1")
mymatrix[,2] <- c("A","A","A","A","A","A","A")
mymatrix[,3] <- c(1,0,0,15,1,2,13)
mymatrix[,4] <- c("baseline","followup","baseline","followup","baseline","followup","followup")
> mymatrix
Patient marker Number Visit
1 B1 A 1 baseline
2 B1 A 0 followup
3 C1 A 0 baseline
4 C1 A 15 followup
5 D1 A 1 baseline
6 D1 A 2 followup
7 D1 A 13 followup
If I do dcast on the first 6 rows I get:
> dcast(mymatrix[1:6,], Patient +marker~Visit, value.var = "Number")
Patient marker baseline followup
1 B1 A 1 0
2 C1 A 0 15
3 D1 A 1 2
If I do dcast on all the rows I get:
> dcast(mymatrix, Patient +marker~Visit, value.var = "Number")
Aggregation function missing: defaulting to length
Patient marker baseline followup
1 B1 A 1 1
2 C1 A 1 1
3 D1 A 1 2
Is there a way instead of defaulting to length it would add a second followup column? So the data would show as follows:
Patient marker baseline followup.1 followup.2
1 B1 A 1 0 NA
2 C1 A 0 15 NA
3 D1 A 1 2 13
Thanks!

Answer 1

It's not clear what you asking, because it seems like you want to combine two different functions in dcast at the same time. It seems to me that you want to improve your first output instead of the second. If so, a simple solution would be just to add an automatic index to the values in the Visit column and then dcast. Here's a simple approach using the data.table package (thought the output is not exactly what you want because I've also added an index to baseline, but it can get you started)
library(data.table)
setDT(mymatrix)[, Visit := paste(Visit, seq_len(.N), sep = "."), list(Patient, Visit)]
dcast.data.table(mymatrix, Patient + marker ~ Visit, value.var = "Number")
# Patient marker baseline.1 followup.1 followup.2
# 1: B1 A 1 0 NA
# 2: C1 A 0 15 NA
# 3: D1 A 1 2 13

Answer 2

You could also use base R
d1 <- transform(mymatrix, Visit=paste0(Visit,ave(seq_along(Number),
Patient, Visit, FUN=seq_along)) )
reshape(d1, idvar=c('Patient', 'marker'), timevar='Visit', direction='wide')
# Patient marker Number.baseline1 Number.followup1 Number.followup2
#1 B1 A 1 0 NA
#3 C1 A 0 15 NA
#5 D1 A 1 2 13
Or dplyr/tidyr
library(dplyr)
library(tidyr)
mymatrix %>%
group_by(Patient, Visit) %>%
mutate(indx=row_number()) %>%
ungroup() %>%
unite(Visit1, Visit, indx) %>%
spread(Visit1, Number)
# Patient marker baseline_1 followup_1 followup_2
#1 B1 A 1 0 NA
#2 C1 A 0 15 NA
#3 D1 A 1 2 13