assigning differences in a loop

Lacking your data, which I presume is ECG measurement information from
the acronyms in use, you could do something like this:

for(i in c("13","26","38")) { 
    for (j in c("HR","PQ","QRS","QT")){
       nam1<-paste("d",j,i,sep="")
       nam2<-paste(j,i,sep=".")
       nam3<-paste(j,"0",sep=".")
       eval(parse(text = paste(nam1, " <- ", nam2, " - ", nam3,  "\n")))
      }}

Quick correction here. I accidentally left in the 'newline' in the last
line above. This is a remnant of testing with print(). It should be:

for(i in c("13","26","38")) { 
    for (j in c("HR","PQ","QRS","QT")){
       nam1<-paste("d",j,i,sep="")
       nam2<-paste(j,i,sep=".")
       nam3<-paste(j,"0",sep=".")
       eval(parse(text = paste(nam1, " <- ", nam2, " - ", nam3)))
      }}


Marc