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If I want to randomly select some samples from different groups I use the plyr package and the code below require(plyr) sampleGroup<-function(df,size) { df[sample(nrow(df),size=size),] } iris.sample<-ddply(iris,.(Species),function(df) sampleGroup(df,10)) Here 10 samples are selected from each species. Some of my dataframes are very big and my question is can I use the same sampleGroup function with the dplyr package? Or is there another way to do the same in dplyr? EDIT Version 0.2 of the dplyr package introduced two new functions to select random rows from a table sample_n and sample_frac

From these questions - Random sample of rows from subset of an R dataframe & Sample random rows in dataframe I can easily see how to randomly sample (select) 'n' rows from a df, or 'n' rows that originate from a specific level of a factor within a df. Here are some sample data: df <- data.frame(matrix(rnorm(80), nrow=40)) df$color <- rep(c("blue", "red", "yellow", "pink"), each=10) df[sample(nrow(df), 3), ] #samples 3 random rows from df, without replacement. To e.g. just sample 3 random rows from 'pink' color - using library(kimisc) : library(kimisc) sample.rows(subset(df, color == "pink"), 3

In some code I want to choose n random numbers in [0,1) which sum to 1 . I do so by choosing the numbers independently in [0,1) and normalizing them by dividing each one by the total sum: numbers = [random() for i in range(n)] numbers = [n/sum(numbers) for n in numbers] My "problem" is, that the distribution I get out is quite skew. Choosing a million numbers not a single one gets over 1/2 . By some effort I've calculated the pdf, and it's not nice. Here is the weird looking pdf I get for 5 variables: Do you have an idea for a nice algorithm to choose the numbers, that result in a more uniform

Is it possible to show me a sample http session with range requests. I mean what would be the request and response headers? The following exchange is between Chrome and a static web server, retrieving an MP4 video. Initial request - for the video. Note the Accept-Ranges response header to indicate the server has range header support: GET /BigBuckBunny_320x180.mp4 Cache-Control: max-age=0 Connection: keep-alive Accept-Language: en-GB,en-US,en Host: localhost:8080 Range: Accept: text/html,application/xhtml+xml,application/xml,*/* User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.7 ...

I want to send a simple string data such as 'a' from an android device to other one via bluetooth. I looked sample bluetooth code in android sdk but it is so complex for me. I cannot understand how I can send only specific data when I press a button. How can I solve this problem? eleven private OutputStream outputStream; private InputStream inStream; private void init() throws IOException { BluetoothAdapter blueAdapter = BluetoothAdapter.getDefaultAdapter(); if (blueAdapter != null) { if (blueAdapter.isEnabled()) { Set<BluetoothDevice> bondedDevices = blueAdapter.getBondedDevices(); if