I'm doing the following in order to import some txt tables and keep them as list:
# set working directory - the folder where all selection tables are stored
hypo_selections<-list.files() # change object name according to each species
hypo_list<-lapply(hypo_selections,read.table,sep="\t",header=T) # change object name according to each species
I want to access one specific element, let's say hypo_list[1]. Since each element represents a table, how should I procced to access particular cells (rows and columns)?
I would like to do something like it:
a<-hypo_list[1]
a[1,2]
But I get the following error message:
Error in a[1, 2] : incorrect number of dimensions
Is there a clever way to do it?
Indexing a list is done using double bracket, i.e. hypo_list[[1]] (e.g. have a look here: http://www.r-tutor.com/r-introduction/list). BTW: read.table does not return a table but a dataframe (see value section in ?read.table). So you will have a list of dataframes, rather than a list of table objects. The principal mechanism is identical for tables and dataframes though.
Note: In R, the index for the first entry is a 1 (not 0 like in some other languages).
Dataframes
l <- list(anscombe, iris) # put dfs in list
l[[1]] # returns anscombe dataframe
anscombe[1:2, 2] # access first two rows and second column of dataset
[1] 10 8
l[[1]][1:2, 2] # the same but selecting the dataframe from the list first
[1] 10 8
Table objects
tbl1 <- table(sample(1:5, 50, rep=T))
tbl2 <- table(sample(1:5, 50, rep=T))
l <- list(tbl1, tbl2) # put tables in a list
tbl1[1:2] # access first two elements of table 1
Now with the list
l[[1]] # access first table from the list
1 2 3 4 5
9 11 12 9 9
l[[1]][1:2] # access first two elements in first table
1 2
9 11