如果每个数据帧具有多于 n 行，则 R 循环用于在数据帧列表中添加数据帧

Question

I usually code in python and I'm struggling with this problem.

I have a list of dataframe names called dataframe_name and I would like to use this list to call some dataframes objects. After that I want to use an if loop to pick up the dataframes with number of rows equal to 34 and list them in order to create a list of dataframe objects.

dataframe_name<-c("x1","x2","x3","x4","x5","x6","x7")
dataframe_list<-list()

for(i in dataframe_name){
  if(nrow(get(i))==34){
    append(get(i),dataframe_list)
  }
}

When I run the script I get this error:

Error in if (nrow(get(i)) == 34) { : argument is of length zero

What I have understood is that nrow(get(i)) appears to be null but I don't know why.

Thanks for any help.

Answer 1

You can try the following R code:

dataframe_name<-c("x1","x2","x3")
x1 <- data.frame(a=c(1, 2))
x2 <- data.frame(a=c(1, 2))
x3 <- data.frame(a=rep(1, 34))
dataframe_list<-list()

for(i in seq_along(dataframe_name)){ #note the different syntax for for loops in R
  if(nrow(get(dataframe_name[i]))==34){
    dataframe_list[[dataframe_name[i]]] <- get(dataframe_name[i]) #new element of the list by the original name of the dataframe
  }
}