subset

I have a data.table with a logical column. Why the name of the logical column can not be used directly for the i argument? See the example. dt <- data.table(x = c(T, T, F, T), y = 1:4) # Works dt[dt$x] dt[!dt$x] # Works dt[x == T] dt[x == F] # Does not work dt[x] dt[!x] mnel From ?data.table Advanced: When i is a single variable name, it is not considered an expression of column names and is instead evaluated in calling scope. So dt[x] will try to evaluate x in the calling scope (in this case the global environment) You can get around this by using ( or { or force dt[(x)] dt[{x}] dt[force(x)]

Let's say I have the following server.R file in shiny: shinyServer(function(input, output) { output$plot <- renderPlot({ data2 <- data[data$x == input$z, ] # subsetting large dataframe plot(data2$x, data2$y) }) output$table <- renderTable({ data2 <- data[data$x == input$z, ] # same subset. Oh, boy... summary(data2$x) }) }) What can I do in order to not have to run data2 <- data[data$x == input$z, ] within every render call? If I do the following, I get a "object of type 'closure' is not subsettable" error: shinyServer(function(input, output) { data2 <- reactive(data[data$x == input$z, ])

I am having trouble subsetting my data. I want the data subsetted on column x, where the first 3 characters begin G45. My data frame: x <- c("G448", "G459", "G479", "G406") y <- c(1:4) My.Data <- data.frame (x,y) I have tried: subset (My.Data, x=="G45*") But I am unsure how to use wildcards. I have also tried grep() to find the indicies: grep ("G45*", My.Data$x) but it returns all 4 rows, rather than just those beginning G45, probably also as I am unsure how to use wildcards. It's pretty straightforward using [ to extract: grep will give you the position in which it matched your search pattern

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<Parameter> parameters; And a array of strings i want to check it against. string[] myStrings = new string[] { "one", "two"}; I want to iterate over the parameter list and check if the source property is equal to any of the myStrings array. I can do this with nested foreach's but i would like to learn how to do it in a nicer way as i have been playing around with linq and like the extension methods on enumerable like

I am having trouble figuring out the proper way to define the [ , $ , and [[ subset operators for an S4 class. Can anyone provide me with a basic example of defining these three for an S4 class? Discover the generic so that we know what we are aiming for > getGeneric("[") standardGeneric for "[" defined from package "base" function (x, i, j, ..., drop = TRUE) standardGeneric("[", .Primitive("[")) <bytecode: 0x32e25c8> <environment: 0x32d7a50> Methods may be defined for arguments: x, i, j, drop Use showMethods("[") for currently available ones. Define a simple class setClass("A", representation