R help - Apr 2013 - Looping through names of both dataframes and column-names

Hello all,

This seems like a pretty standard question - suppose I want to loop through
a set of similar data-frames, with similar variables, and create new
variables within them:

nl<-seq(1,5)for (i in nl) {
  assign(paste0("df_",nl[i]),data.frame(x=seq(1:10),y=rnorm(10)))}
ls()[grep("df_",ls())]
nls<-ls()[grep("df_",ls())]for (df in nls) {
  print(df)
  for (var in names(get(df))) {
    print(var)
   
assign(paste0(df,"$",paste0(var,"_cs")),cumsum(get(df)[[var]]))
  }}
ls()[grep("df_",ls())]

The code above *almost* works, except that it creates a whole bunch of
objects of the form df_1$x_cs,df_1$yx_cs ..... What I want is 5 dataframes,
with the $ elements enclosed, as usual.

Any help or guidance would be appreciated.

Much thanks,
Dan

	[[alternative HTML version deleted]]

Here are two possible ways to do it:

This would simplify your code a bit. But it changes the names of x_cs to
cs.x. 
for (df in nls) {
  assign(df, cbind(get(df), cs=apply(get(df), 2, cumsum)))
  }

This is closer to what you have done. 
for (df in nls) {
  print(df)
  for (var in names(get(df))) {
    print(var)
    assign(df, within(get(df), assign(paste0(var,"_cs"),
cumsum(get(df)[[var]]))))
  }}
ls()[grep("df_",ls())]

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Daniel Egan
Sent: Donnerstag, 25. April 2013 22:19
To: r-help at r-project.org
Subject: [R] Looping through names of both dataframes and column-names

Hello all,

This seems like a pretty standard question - suppose I want to loop
through a set of similar data-frames, with similar variables, and create
new variables within them:

nl<-seq(1,5)for (i in nl) {
  assign(paste0("df_",nl[i]),data.frame(x=seq(1:10),y=rnorm(10)))}
ls()[grep("df_",ls())]
nls<-ls()[grep("df_",ls())]for (df in nls) {
  print(df)
  for (var in names(get(df))) {
    print(var)
   
assign(paste0(df,"$",paste0(var,"_cs")),cumsum(get(df)[[var]]))
  }}
ls()[grep("df_",ls())]

The code above *almost* works, except that it creates a whole bunch of
objects of the form df_1$x_cs,df_1$yx_cs ..... What I want is 5
dataframes, with the $ elements enclosed, as usual.

Any help or guidance would be appreciated.

Much thanks,
Dan

	[[alternative HTML version deleted]]

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