mean

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: I'm learning Objectiv C, and I hear the term "live in the heap" constantly, from what I understand its some kind of unknown area that a pointer lives in, but trying to really put head around the exact term...like "we should make our property strong so it won't live in the heap. He said that since the property is private. I know it'ss a big difference It's pretty clear that we want to make sure that we want to count the reference to this object so the autorelease wont clean it (we want to "retain" it from what i know so far), but I

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am trying to figure out why I am getting an error message when using ddply. Example data: data<-data.frame(area=rep(c("VA","OC","ES"),each=4), sex=rep(c("Male","Female"),each=2,times=3), year=rep(c(2009,2010),times=6), bin=c(110,120,125,125,110,130,125,80,90,90,80,140), shell_length=c(.4,4,1,2,.2,5,.4,4,.8,4,.3,4)) bin7<-ddply(data, .(area,year,sex,bin), summarize,n_bin=length(shell_length)) Error message: Error in .fun(piece, ...) : argument "by" is missing, with no default I got this error message yesterday. I restarted R and reran the

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have a numpy matrix A where the data is organised column-vector-vise i.e A[:,0] is the first data vector, A[:,1] is the second and so on. I wanted to know whether there was a more elegant way to zero out the mean from this data. I am currently doing it via a for loop: mean=A.mean(axis=1) for k in range(A.shape[1]): A[:,k]=A[:,k]-mean So does numpy provide a function to do this? Or can it be done more efficiently another way? 回答1: As is typical, you can do this a number of ways. Each of the approaches below works by adding a dimension to

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I found some code to start spark locally with: val conf = new SparkConf().setAppName("test").setMaster("local[*]") val ctx = new SparkContext(conf) What does the [*] mean? 回答1: From the doc : ./bin/spark-shell --master local[2] The --master option specifies the master URL for a distributed cluster, or local to run locally with one thread, or local[N] to run locally with N threads. You should start by using local for testing. And from here : local[*] Run Spark locally with as many worker threads as logical cores on your machine. 回答2: Master

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I have come across the term O(log* N) in a book I'm reading on data structures. What does log* mean? I cannot find it on Google , and WolframAlpha doesn't understand it either . 回答1: It's iterated logarithm. See here for a description of lots of different time complexities, and here for more details on the iterated logarithm itself. The iterated logarithm is the number of times the logarithm has to be applied before the result becomes one or less. 回答2: It's called iterated logarithm function . It is a very slowly growing function. For

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am trying to generate exponentially distributed random number with mean equal to 1. I know how to get random number for normal distribution with mean and standard deviation. We can get it by normal(mean, standard_deviation) , but I don't know how to get random number for exponential distribution. Can anyone help me with this? 回答1: With C++11 the standard actually guarantees that there is a RNG following the requirements of exponential-distribution available in the STL, and fittingly the object-type has a very descriptive name. The mean in

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am new to nodejs and i had just installed bower module globally. Ever since then, npm list command gives the following output which I searched for on the web but couldn't find any help : **npm ERR! invalid: chalk@0.5.1 /usr/local/lib/node_modules/bower/node_modules/chalk npm ERR! invalid: ansi-regex@0.2.1 /usr/local/lib/node_modules/bower/node_modules/chalk/node_modules/has-ansi/node_modules/ansi-regex npm ERR! invalid: configstore@0.3.1 /usr/local/lib/node_modules/bower/node_modules/update-notifier/node_modules/configstore npm ERR!

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I started by generating a sample of 500 uniformly-distributed random numbers between 0 and 1 using the code below: set.seed(1234) X<-runif(500, min=0, max=1) Now, I need to write a psuedocode that generates 10000 samples of N=500 for a MC simulation, compute the mean of my newly created X, and store the iteration number and mean value in a result object. I have never attempted this, and so far I have this: n.iter <-(10000*500) results <- matrix (0, n.iter, 4) Finally, once this is accomplished, I'm to run it, then obtain median, mean, and

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: This question already has an answer here: Mean per group in a data.frame [duplicate] 8 answers I have a dataframe recording how much money a costomer spend in detail like the following: custid, value 1, 1 1, 3 1, 2 1, 5 1, 4 1, 1 2, 1 2, 10 3, 1 3, 2 3, 5 How to calcuate the charicteristics using mean,max,median,std, etc like the following? Use some apply function? And how? custid, mean, max,min,median,std 1, .... 2,.... 3,.... 回答1: To add to the alternatives, here's summaryBy from the "doBy" package, with which you can specify a list of

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: This question already has an answer here: Mean per group in a data.frame [duplicate] 8 answers I have a dataframe recording how much money a costomer spend in detail like the following: custid, value 1, 1 1, 3 1, 2 1, 5 1, 4 1, 1 2, 1 2, 10 3, 1 3, 2 3, 5 How to calcuate the charicteristics using mean,max,median,std, etc like the following? Use some apply function? And how? custid, mean, max,min,median,std 1, .... 2,.... 3,.... 回答1: To add to the alternatives, here's summaryBy from the "doBy" package, with which you can specify a list of