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问题 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

问题 Is it possible to show me a sample http session with range requests. I mean what would be the request and response headers? 回答1: 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

问题 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? 回答1: private OutputStream outputStream; private InputStream inStream; private void init() throws IOException { BluetoothAdapter blueAdapter = BluetoothAdapter.getDefaultAdapter(); if (blueAdapter != null) { if

问题 IE10+ no longer supports browser detection tags to identify a browser. For detecting IE10 I am using JavaScript and a capability-testing technique to detect certain ms prefixed styles are defined such as msTouchAction and msWrapFlow . I want to do the same for IE11, but I am assuming that all the IE10 styles will be supported in IE11 as well. Can anyone help me identify IE11 only styles or capabilities that I could use to tell the two apart? Extra Info I don\'t want to use User Agent type

问题 I am struggling to find the appropriate function that would return a specified number of rows picked up randomly without replacement from a data frame in R language? Can anyone help me out? 回答1: First make some data: > df = data.frame(matrix(rnorm(20), nrow=10)) > df X1 X2 1 0.7091409 -1.4061361 2 -1.1334614 -0.1973846 3 2.3343391 -0.4385071 4 -0.9040278 -0.6593677 5 0.4180331 -1.2592415 6 0.7572246 -0.5463655 7 -0.8996483 0.4231117 8 -1.0356774 -0.1640883 9 -0.3983045 0.7157506 10 -0.9060305

问题 I\'ve just started using R and I\'m not sure how to incorporate my dataset with the following sample code: sample(x, size, replace = FALSE, prob = NULL) I have a dataset that I need to put into a training (75%) and testing (25%) set. I\'m not sure what information I\'m supposed to put into the x and size? Is x the dataset file, and size how many samples I have? 回答1: There are numerous approaches to achieve data partitioning. For a more complete approach take a look at the createDataPartition