CODEWITHSUNDEEP
rlistdataframerowcol
user6450579
user6450579

Reputation:

R - remove last row and convert row in column in dataframes within a list

I need your help as I have to:

Here an example of one of my dataframes:

         V1        V2        V3
2         7002                    
8  14 Feb 1959    47.664     1.310
9  25 Aug 1960   680.615     3.790
10 08 Aug 1961   287.893     2.490
11 11 Feb 1962   405.366     2.920
12 14 Dec 1962   312.010     2.560
13 18 Aug 1964   167.684     1.930

    [....]

53 19 Jan 2004   385.980     2.835
54 13 Jun 2005   415.942     2.939
55 26 Nov 2005   280.773     2.431
56       [END]

So, in this case, add 7002 as new column and remove the 56th row. I have got ~290 dataframes in my list.

Thanks Paolo

Upvotes: 1

Views: 1430

Answers (2)

tester
tester

Reputation: 1692

If all your dataframes look the same you could use something similar to that:

df1 <- data.frame(matrix(data =  (rnorm(9)), 3, 3))
df2 <- data.frame(matrix(data =  (100:108), 3, 3))
colnames(df1) <- c("V1", "v2", "V3")
colnames(df2) <- c("V1", "v2", "V3")

list1 <- list(df1, df2)
list2 <- list1

for(i in 1:length(list2)) {
  list2[[i]] <- list2[[i]][-length(list2[[i]]), ]
  colnumber <- dim(list2[[i]])[2] + 1
  list2[[i]]$V4 <- list2[[i]][1, 1]
}

list2

However, if you have a more complicated structure or the values are not in the same spot in every dataframe, you will have to look for a dplyr or apply-solution or even write your own function for doing so.

I hope it helps.

Upvotes: 0

akrun
akrun

Reputation: 887148

We can use lapply to loop over the list, remove the last row (x[-nrow(x),]), and create a new column with the first cell value.

lst1 <- lapply(lst, function(x) transform(x[-nrow(x),], NewCol = x[1,1]))

Upvotes: 3

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