Dear Amelia community, I am a new Amelia user and I have been trying to use Amelia but could not understand how to run Amelia on a data from a study that has a within subject and a between subject variable. Below I will try to explain my situation with a hypothetical experiment and data. Experiment: Let's assume I am interested to see the reaction time of subjects to some stimulus (say they have to identify the heaviest of the objects been placed on their left and right hands) under either a neutral or a happy setting (I the later case the subjects are provided with their choice of drinks and a snack). Added to this, each subject is tested with a range of weights. And I am interested to see if the subjects with the "happy" atmosphere can perform well than the "neutral" ones. Here is the R code that makes the data for the above experiment: # ===================================================== # Create a dataframe to contain the subject name and the repeated measures factor Stimulus intensity mydata=data.frame(SubjectName=sort(rep(paste("Subject",1:8,sep="_"),8)),StimIntensity=(rep(seq(100,800,by=100)))); # Add the between subjects variable Group mydata = cbind(mydata,Group=sort(rep(c("Neutral","Happy"),32),decreasing=T)); # Creates the Response time values for first group : "Neutral" i=0;k=0;while (i < 4) {a[((i*8)+1):((i*8)+8)]=sort(rnorm(mean=10+(i*10):20+(i*10),1,n=8)); i = i+1;}; # Creates the Response time values for the second group : "Happy" i=0;b=0;while (i < 4) {b[((i*8)+1):((i*8)+8)]=sort(rnorm(mean=10+(i*10):20+(i*10),1,n=8))*c(1,1,1,1,1,1.5,1.75,2); i = i+1;}; # Add the data to the RT column in mydata dataframe mydata=cbind(mydata,"RT"=c(a,b)); # Creates a second dataframe with missing data (n=15) mydataMissing = mydata; mydataMissing[runif(n=15,min=1,max=64),"RT"] = NA; # ===================================================== As you can see I have also made an additional data fame that has the missing data. The question is how do I run Amelia in this case. Any help would be appreciated. I guess the cross section variable would be "Group" and the time series variable = "StimIntensity" but when I just provide only these it produces the error below. "amelia starting Amelia Error Code: 61 There is only 1 column of data after removing the ts, cs and idvars. Cannot impute without adding polytime." Thanks in advance Best -Anup