Two levels of longitudinal data: how to change the shape?

Question

I have a dataset with several time points for the hippocampus volume for each object. Each volume of the hippocampus has a left and right dimension. Now I want to compare the longitudinal changes left and right. I know how to change my data to temporary points, but I don’t know how to add “side” levels to them.

So here is my reproducible dataset:

mydata <- data.frame(SID=sample(1:150,400, replace=TRUE), hippLeft_T1=sample(6000:8000,400,replace=TRUE), hippRight_T1=sample(6000:8000,400,replace=TRUE),hippLeft_T2=sample(6000:8000,400,replace=TRUE), hippRight_T2=sample(6000:8000,400,replace=TRUE),hippLeft_T3=sample(6000:8000,400,replace=TRUE), hippRight_T3=sample(6000:8000,400,replace=TRUE))

Then I would change it in the longitudinal direction:

long <- reshape(mydata, direction="long", varying=list(c(2,4,6),c(3,5,7)),idvar="SID", timevar="time", v.names=c("HippLeft","HippRight"), times=c("time1","time2","time3"))

Do I have to apply reshape twice to get levels for left and right there? Or is there another way to do this? Thank!

** What I'm trying to get is the following:

Answer 1

- unite, gather separate tidyr:

library(tidyr)
long <- mydata %>% unite("times1", hippLeft_T1,hippRight_T1) %>%
                   unite("times2", hippLeft_T2,hippRight_T2) %>%
                   unite("times3", hippLeft_T3,hippRight_T3) %>%
                   gather("times","Hipp",times1:times3) %>%
                   separate(Hipp,c("Left","Right")) %>%
                   gather("Side","Hipp",Left:Right)

:

• unite T1, T2 T3 times1, times2 times3
• gather , times Hipp
• separate Hipp Left Right
• gather Left Right, Side Hipp

- gather, :

library(tidyr)
long <- mydata %>% unite("Left", hippLeft_T1,hippLeft_T2,hippLeft_T3) %>%
                   unite("Right", hippRight_T1,hippRight_T2,hippRight_T3) %>%
                   gather("Side","Hipp",Left:Right) %>%
                   separate(Hipp,c("times1","times2","times3")) %>%
                   gather("times","Hipp",times1:times3)

, gather:

library(dplyr)
library(tidyr)
long <- mydata %>% gather("Side","Hipp",-SID) %>%
                   mutate(times=paste0("times",sub(".*(\\d)$","\\1",Side)),
                          Side=sub("^hipp([A-z]+)_T.*","\\1",Side)) %>%
                   select(SID,Side,times,Hipp)

Side gather , mydata. deployer::mutate times. sub , times Left, Right Side.

123, :

set.seed(123)
mydata <- data.frame(SID=sample(1:150,400, replace=TRUE), hippLeft_T1=sample(6000:8000,400,replace=TRUE), hippRight_T1=sample(6000:8000,400,replace=TRUE),hippLeft_T2=sample(6000:8000,400,replace=TRUE), hippRight_T2=sample(6000:8000,400,replace=TRUE),hippLeft_T3=sample(6000:8000,400,replace=TRUE), hippRight_T3=sample(6000:8000,400,replace=TRUE))
head(mydata)
##  SID hippLeft_T1 hippRight_T1 hippLeft_T2 hippRight_T2 hippLeft_T3 hippRight_T3
##1  44        7973         6941        7718         7279        6319         7465
##2 119        6274         6732        7775         6249        6289         7220
##3  62        7811         6242        6978         6510        6298         6448
##4 133        7153         6094        7436         7641        7029         7833
##5 142        6791         6525        6973         7608        6986         7606
##6   7        6900         7938        7978         6091        7233         6625

:

print(long)
##     SID  Side  times Hipp
##   1  44  Left times1 7973
##   2 119  Left times1 6274
##   3  62  Left times1 7811
##   4 133  Left times1 7153
##   5 142  Left times1 6791
##   6   7  Left times1 6900
## ...
## 401  44 Right times1 6941
## 402 119 Right times1 6732
## 403  62 Right times1 6242
## 404 133 Right times1 6094
## 405 142 Right times1 6525
## 406   7 Right times1 7938
## ...
## 801  44  Left times2 7718
## 802 119  Left times2 7775
## 803  62  Left times2 6978
## 804 133  Left times2 7436
## 805 142  Left times2 6973
## 806   7  Left times2 7978
## ...
##1201  44 Right times2 7279
##1202 119 Right times2 6249
##1203  62 Right times2 6510
##1204 133 Right times2 7641
##1205 142 Right times2 7608
##1206   7 Right times2 6091
## ...
##1601  44  Left times3 6319
##1602 119  Left times3 6289
##1603  62  Left times3 6298
##1604 133  Left times3 7029
##1605 142  Left times3 6986
##1606   7  Left times3 7233
## ...
##2001  44 Right times3 7465
##2002 119 Right times3 7220
##2003  62 Right times3 6448
##2004 133 Right times3 7833
##2005 142 Right times3 7606
##2006   7 Right times3 6625