Question

The following is sample data and part of function I have trouble with.

# data
Gr1 <- data.frame (group = rep(1:2, each = 2001), 
position = round (c(0, cumsum (rnorm (2000, 0.05, 0.08)), 0, 
cumsum (rnorm (2000, 0.05, 0.08)))))

 Gr2 <- data.frame (group = rep(1:2, each = 2001), 
 position = round (c(0, cumsum (rnorm (2000, 0.05, 0.08)), 0, 
  cumsum (rnorm (2000, 0.04, 0.08)))))

 Gr3 <- data.frame (group = rep(1:2, each = 2001), 
position = round (c(0, cumsum (rnorm (2000, 0.05, 0.08)), 0, 
 cumsum (rnorm (2000, 0.05, 0.08)))))

 groupobs = list(Gr1, Gr2, Gr3)
 grnames = c("A", "B", "C")
 spacing = c(0, 0.1, 0.3)


    # for loop 

    for (i in 1:length(groupobs)){
     groupobs[i]$sgrp <- grnames[i]
     groupobs[i]$y <-  groupobs[i]$group + spacing[i]
    }

    # binding of list components
    mydf <- data.frame (rbind (groupobs)

How can I achieve this ?

Edit: With above loop, I want to achieve the following manual process. I want to automate n number of dataframe, so that I do not need to write a lengthy steps:

Please note that each of dataframes in this have same name of variables. For each component dataframe I want perform the following tasks. If I do it without looping:

# for first dataframe with in list 
Gr1$sgrp <- grnames[1]
Gr1$y <- Gr1$group + spacing[1]

# for second dataframe in the list
Gr2$sgrp <- grnames[2]
Gr2$y <- Gr1$group + spacing[2]

# for third dataframe in the list
Gr3$sgrp <- grnames[3]
Gr3$y <- Gr1$group + spacing[3]

mydf <- data.frame (rbind (Gr1, Gr2, Gr3))

Answer 1

I maybe be way off here but

mydf<-mapply(function(a,b,c){a$sgrp<-b;a$y<-c;a},groupobs,grnames,spacing,SIMPLIFY = F)
mydf<-do.call("rbind",mydf)
> str(mydf)
'data.frame':   12006 obs. of  4 variables:
 $ group   : int  1 1 1 1 1 1 1 1 1 1 ...
 $ position: num  0 0 0 0 0 0 0 0 0 1 ...
 $ sgrp    : chr  "A" "A" "A" "A" ...
 $ y       : num  0 0 0 0 0 0 0 0 0 0 ...

might be what you are after………….

EDIT: changed to hopefully produce dataframe

thanks to @jon