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Questions tagged [subset]

A subset consists of those elements selected from a larger set of elements, by their position in the larger set or other features, such as their value.

Definition:

From Wikipedia:

a set A is a subset of a set B, or equivalently B is a superset of A, if A is 'contained' inside B, that is, all elements of A are also elements of B.

Uses:

  • In , subset is a function that selects a subset of elements from a vector, matrix, or data frame, given some logical expression (caution: subset drops incomplete cases; see How to subset data in R without losing NA rows?). However, for programmatic use (as opposed to interactive use) it is better to use the \[ (or [[) operators or the filter function from dplyr. substring is used to find subsets of character strings.
  • In , a subset of an array can be obtained with array[indices].
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Why is `[` better than `subset`?

When I need to filter a data.frame, i.e., extract rows that meet certain conditions, I prefer to use the subset function: subset(airquality, Month == 8 & Temp > 90) Rather than the [ function: airquality[airquality$Month == 8 & airquality$Temp >…
flodel
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How to drop columns by name in a data frame

I have a large data set and I would like to read specific columns or drop all the others. data <- read.dta("file.dta") I select the columns that I'm not interested in: var.out <- names(data)[!names(data) %in% c("iden", "name", "x_serv",…
leroux
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Opposite of %in%: exclude rows with values specified in a vector

A categorical variable V1 in a data frame D1 can have values represented by the letters from A to Z. I want to create a subset D2, which excludes some values, say, B, N and T. Basically, I want a command which is the opposite of %in% D2 = subset(D1,…
user702432
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How can I get the intersection, union, and subset of arrays in Ruby?

I want to create different methods for a class called Multiset. I have all the required methods, but I'm unsure of how to write intersection, union, and subset methods. For intersection and union, my code starts like this: def intersect(var) x =…
user487743
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Filter data.frame rows by a logical condition

I want to filter rows from a data.frame based on a logical condition. Let's suppose that I have data frame like expr_value cell_type 1 5.345618 bj fibroblast 2 5.195871 bj fibroblast 3 5.247274 bj fibroblast 4 5.929771 …
lhahne
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Check whether an array is a subset of another

Any idea on how to check whether that list is a subset of another? Specifically, I have List t1 = new List { 1, 3, 5 }; List t2 = new List { 1, 5 }; How to check that t2 is a subset of t1, using LINQ?
Graviton
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How to check if one dictionary is a subset of another larger dictionary?

I'm trying to write a custom filter method that takes an arbitrary number of kwargs and returns a list containing the elements of a database-like list that contain those kwargs. For example, suppose d1 = {'a':'2', 'b':'3'} and d2 = the same thing.…
Jamey
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Selecting data frame rows based on partial string match in a column

I want to select rows from a data frame based on partial match of a string in a column, e.g. column 'x' contains the string "hsa". Using sqldf - if it had a like syntax - I would do something like: select * from <> where x like 'hsa'. Unfortunately,…
Asda
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Subset data frame based on multiple conditions

I wish to filter a data frame based on conditions in several columns. For example, how can I delete rows if column A = B and Column E = 0.
AME
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Check if list contains any of another list

I have a list of parameters like this: public class parameter { public string name {get; set;} public string paramtype {get; set;} public string source {get; set;} } IEnumerable parameters; And a array of strings i want to…
gdp
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Subset of rows containing NA (missing) values in a chosen column of a data frame

We have a data frame from a CSV file. The data frame DF has columns that contain observed values and a column (VaR2) that contains the date at which a measurement has been taken. If the date was not recorded, the CSV file contains the value NA, for…
John
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Select multiple elements from a list

I have a list in R some 10,000 elements long. Say I want to select only elements, 5, 7, and 9. I'm not sure how I would do that without a for loop. I want to do something like mylist[[c(5,7,9]] but that doesn't work. I've also tried the lapply…
user1357015
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How to subset matrix to one column, maintain matrix data type, maintain row/column names?

When I subset a matrix to a single column, the result is of class numeric, not matrix (i.e. myMatrix[ , 5 ] to subset to the fifth column). Is there a compact way to subset to a single column, maintain the matrix format, and maintain the row/column…
Suraj
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Select rows from a data frame based on values in a vector

I have data similar to this: dt <- structure(list(fct = structure(c(1L, 2L, 3L, 4L, 3L, 4L, 1L, 2L, 3L, 1L, 2L, 3L, 2L, 3L, 4L), .Label = c("a", "b", "c", "d"), class = "factor"), X = c(2L, 4L, 3L, 2L, 5L, 4L, 7L, 2L, 9L, 1L, 4L, 2L, 5L, 4L, 2L)),…
Joe King
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How do I extract a single column from a data.frame as a data.frame?

Say I have a data.frame: df <- data.frame(A=c(10,20,30),B=c(11,22,33), C=c(111,222,333)) A B C 1 10 11 111 2 20 22 222 3 30 33 333 If I select two (or more) columns I get a data.frame: x <- df[,1:2] A B 1 10 11 2 20 22 3 30 33 This is…
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