问题
I have a function that outputs a large matrix (Mat1) and a small dataframe (Smalldf1) I store them in a list called "Result". This function is run inside a loop so I create many versions of my "Result" list until my loop ends....each time I add them to a list called "FINAL".
At the end of my loop I end up with a List called FINAL, that has many smaller "Result" lists inside...each containing a small dataframe and a large Matrix.
I want to rbind all of the small dataframes together to form one larger dataframe and call it DF1 - I'm not sure how I access these now that I'm accessing a list within a list..?
A similar question on here gave a solution like this:
DF1 <- do.call("rbind",lapply(FINAL, function(x) x["Smalldf1"]))
However this gives the output as a single column called "Smalldf1" with the description of Smalldf1...ie this is literally printed in the column list(X1="xxx", X2="xxx", X3="xxx")...I need this broken out to look like the original format, 3 columns housing the information...?
Any help would be great.
回答1:
I make my comment into an answer. This could be your data:
df <- data.frame(X1=1:3, X2=4:6, X3=7:9)
FINAL=list(Result=list(Smalldf1=df, Mat1=as.matrix(df)),
Result=list(Smalldf1=df+1, Mat1=as.matrix(df+1)))
You can combine lapply to extract the first (or Nth, just change the 1) elements of the nested lists, and then do a rbind on this result, either with do.call or with dplyr:
#### # Doing it in base R:
do.call("rbind", lapply(FINAL, "[[", 1) )
#### # Or doing it with dplyr:
library(dplyr)
lapply(FINAL, "[[", 1) %>% bind_rows
#### X1 X2 X3
#### 1 1 4 7
#### 2 2 5 8
#### 3 3 6 9
#### 4 2 5 8
#### 5 3 6 9
#### 6 4 7 10
This should be your expected result
WARNING:
The solution using dplyr doesn't work for old versions of dplyr (i tested it on dplyr_0.5.0, but it returns an error on dplyr_0.2 for instance)
来源：https://stackoverflow.com/questions/40082625/extract-then-row-bind-data-frames-from-nested-lists