subset

I am trying to write a function in R which takes 3 inputs: Directory pollutant id I have a directory on my computer full of CSV's files i.e. over 300. What this function would do is shown in the below prototype: pollutantmean <- function(directory, pollutant, id = 1:332) { ## 'directory' is a character vector of length 1 indicating ## the location of the CSV files ## 'pollutant' is a character vector of length 1 indicating ## the name of the pollutant for which we will calculate the ## mean; either "sulfate" or "nitrate". ## 'id' is an integer vector indicating the monitor ID numbers ## to be

Is there a way for me to subset data based on column names starting with a particular string? I have some columns which are like ABC_1 ABC_2 ABC_3 and some like XYZ_1, XYZ_2,XYZ_3 let's say. How can I subset my df based only on columns containing the above portions of text (lets say, ABC or XYZ )? I can use indices, but the columns are too scattered in data and it becomes too much of hard coding. Also, I want to only include rows from each of these columns where any of their value is >0 so if either of the 6 columns above has a 1 in the row, it makes a cut into my final data frame. Try grepl

I want to find the subsets of a set of integers. It is the first step of "Sum of Subsets" algorithm with backtracking. I have written the following code, but it doesn't return the correct answer: BTSum(0, nums); ///************** ArrayList<Integer> list = new ArrayList<Integer>(); public static ArrayList<Integer> BTSum(int n, ArrayList<Integer> numbers) { if (n == numbers.size()) { for (Integer integer : list) { System.out.print(integer+", "); } System.out.println("********************"); list.removeAll(list); System.out.println(); } else { for (int i = n; i < numbers.size(); i++) { if (i ==