lapply

I've been messing around with this for some time. I recently started using the quantmod package to perform analytics on stock prices. I have a ticker vector that looks like the following: > tickers [1] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" "XLI" "XLB" "XLK" "XLU" "XLV" [14] "QQQ" > str(tickers) chr [1:14] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" ... I wrote a function called myX to use in a lapply call to save prices for every stock in the vector tickers. It has the following code: myX <- function(tickers, start, end) { require(quantmod) getSymbols(tickers, from=start, to=end)

This is part of the dataset (named "ME1") I'm using (all variables are numeric): Year AgeR rateM 1 1751 -1.0 0.241104596 2 1751 -0.9 0.036093609 3 1751 -0.8 0.011623734 4 1751 -0.7 0.006670552 5 1751 -0.6 0.006610552 6 1751 -0.5 0.008510828 7 1751 -0.4 0.009344041 8 1751 -0.3 0.011729740 9 1751 -0.2 0.010988005 10 1751 -0.1 0.015896107 11 1751 0.0 0.018190140 12 1751 0.1 0.024588340 13 1751 0.2 0.029801362 14 1751 0.3 0.044515912 15 1751 0.4 0.055240354 16 1751 0.5 0.088476758 17 1751 0.6 0.119045309 18 1751 0.7 0.167866571 19 1751 0.8 0.239244825 20 1751 0.9 0.329683010 21 1751 1.0 0

I have numerous csv files in multiple directories that I want to read into a R tribble or data.table. I use "list.files()" with the recursive argument set to TRUE to create a list of file names and paths, then use "lapply()" to read in multiple csv files, and then "bind_rows()" stick them all together: filenames <- list.files(path, full.names = TRUE, pattern = fileptrn, recursive = TRUE) tbl <- lapply(filenames, read_csv) %>% bind_rows() This approach works fine. However, I need to extract a substring from the each file name and add it as a column to the final table. I can get the substring I

R textbooks continue to promote the use of lapply instead of loops. This is easy even for functions with arguments like lapply(somelist, f, a=1, b=2) but what if the arguments change depending on the list element? Assume my somelist consists of: somelist$USA somelist$Europe somelist$Switzerland plus there is anotherlist with the same regions and I want use lapply with these changing arguments? This could be useful when f was a ratio calculation for example. lapply(somelist, f, a= somelist$USA, b=anotherlist$USA) Is there are way except for a loop to run through these regions efficiently? EDIT:

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