Data.table subset by column name
WebSep 11, 2014 · If I have a data table, foo, in R with a column named "date", I can get the vector of date values by the notation foo[, date] (Unlike data frames, date doesn't need to be in quotes). ... You can evaluate names within data.table just by putting them into – David Arenburg. Sep 10, 2014 at 23:10 ... You can also look at the code for subset.data ... WebJun 30, 2024 · How to subset the data frame (DataFrame) by column value and name in R? By using R base df[] notation, or subset() you can easily subset the R Data Frame (data.frame) by column value or by …
Data.table subset by column name
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WebJun 10, 2015 · Update 2024-04-22. data.table has evolved and now iris [ , 'Petal.Length'] will return a one-column table (i.e., character and integer literal vectors in j can be used for column selection). There have also been ample updates in extending .SDcols for common use cases to do column filtration (subsetting by pattern on name, subsetting by logical ... WebNov 3, 2016 · From the data.table help: "By default with=TRUE and j is evaluated within the frame of x; column names can be used as variables. When with=FALSE j is a character vector of column names or a numeric vector of column positions to select, and the value returned is always a data.table." – djhurio Nov 3, 2016 at 10:20
WebSep 4, 2014 · Everything I see explains how to use a variable for j (i.e. column names), but not for i. When I just put the name of the variable in, i.e. setkey (dtpredictions, colA, colB) nextweek = dtpredictions [J (uservar, weekvar)] it returns the entire table. Trying to apply the answer to FAQ 1.6, I tried: WebFeb 16, 2024 · The variable mycol does not exist as a column name of DT so data.table then looked in the calling scope and found mycol there and returned its value "x". This is correct behaviour currently. ... The scope of X’s subset; i.e., X’s column names. The scope of each row of Y; i.e., Y’s column names (join inherited scope)
WebSep 7, 2011 · In data.table you can use the function setcolorder: setcolorder reorders the columns of data.table, by reference, to the new order provided. Here a reproducible example: library (data.table) test = data.table (C = c (0, 2, 4, 7, 8), A = c (4, 2, 4, 7, 8), B = c (1, 3, 8, 3, 2)) setcolorder (test, c (order (names (test)))) test #> A B C #> 1: 4 ... Webdata.table inherits from data.frame . It offers quick subset, fast grouping, express update, fast ordered joins and select pillars to a short and flexible written, fork faster …
WebI am aware of dplyr select() but I seek a solution that doesn't involve typing the column names, and would greatly appreciate a clear method for subsetting a data.table by using a "column number." I have occasionally used subset(), and even gone so far as constructing character vector J for use in data[ I, J, by = K]. I must be missing something.
WebI want to create the equal result as the below smallest reproducible example, but you can watch the subsetting status for the last cipher the basically remove line where .SD … phoenix adult softballWebFeb 16, 2024 · data.table is an R package that provides an enhanced version of data.frame s, which are the standard data structure for storing data in base R. In the Data section … phoenix advertising clubWebFeb 16, 2024 · Secondary indices and auto indexing 2024-02-16. This vignette assumes that the reader is familiar with data.table’s [i, j, by] syntax, and how to perform fast key based subsets. If you’re not familiar with these concepts, please read the “Introduction to data.table”, “Reference semantics” and “Keys and fast binary search based subset” … phoenix advertising jobsWebsubset (Data, Column_X %in% variableData) You can also use dplyr and filter: Data %>% filter (Column_X %in% variableData) Share Improve this answer Follow edited Jul 27, 2024 at 20:48 answered Jul 27, 2024 at 20:29 Alper t. Turker 33.9k 9 81 115 1 This might require variableData be a vector (instead of the list the OP used). phoenix adult foster homesWebSelecting a subset of columns in a data.table (5 answers) Closed 5 years ago. I have a data table with a bunch of columns, e.g.: dt<-data.table (matrix (runif (10*10),10,10)) I want to perform some operation on the data table, such as producing a correlation matrix ( cor … phoenix adult coloring pagesWebdata.table inherits from data.frame . It offers quick subset, fast grouping, express update, fast ordered joins and select pillars to a short and flexible written, fork faster development. It is inspired by A[B] layout in Rwhere A is a matrix and B is an 2-column matrix. phoenix adriatic skyWebJan 31, 2013 · 60 I have a data.table with a character column, and want to select only those rows that contain a substring in it. Equivalent to SQL WHERE x LIKE '%substring%' E.g. > Months = data.table (Name = month.name, Number = 1:12) > Months ["mb" %in% Name] Empty data.table (0 rows) of 2 cols: Name,Number how do you close this pc