Join multiple dataframes and calculate ratios

There is a function in plyr package called join_all that allows for combining mutliple dataframes into one by using particular columns (variables). Function mutate from dplyr helps to calculatate new variables from existing ones (ratios from intensities in this case).

library(plyr) #join_all
library(dplyr)

togeth01<-join_all(list(longmat1038, longmat1260,longmat1535,longmat1450,longmat1642,longmat1678),
                   by=c("x","y"), type = 'full')
togeth01 <-
  mutate(togeth01,
         ratio1038to1260 = I1038/I1260,
         ratio1038to1450 = I1038/I1450,
         ratio1038to1535 = I1038/I1535,
         ratio1038to1642 = I1038/I1642,
         ratio1038to1678 = I1038/I1678,
         ratio1260to1450 = I1260/I1450,
         )