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): 问题: I have a dataframe with the lengths and widths of various arthropods from the guts of salamanders. Because some guts had thousands of certain prey items, I only measured a subset of each prey type. I now want to replace each unmeasured individual with the mean length and width for that prey. I want to keep the dataframe and just add imputed columns (length2, width2). The main reason is that each row also has columns with data on the date and location the salamander was collected. I could fill in the NA with a random selection of the measured

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'm new to Pandas.... I've got a bunch of polling data; I want to compute a rolling mean to get an estimate for each day based on a three-day window. As I understand from this question , the rolling_* functions compute the window based on a specified number of values, and not a specific datetime range. Is there a different function that implements this functionality? Or am I stuck writing my own? EDIT: Sample input data: polls_subset.tail(20) Out[185]: favorable unfavorable other enddate 2012-10-25 0.48 0.49 0.03 2012-10-25 0.51 0.48 0.02

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: What does the following do in a Makefile? rule : $ ( deps ) @: I can't seem to find this in the make manual. 回答1: It means "don't echo this command on the output." So this rule is saying "execute the shell command : and don't echo the output. Of course the shell command : is a no-op, so this is saying "do nothing, and don't tell." Why? The trick here is that you've got an obscure combination of two different syntaxes. The make(1) syntax is the use of an action starting with @, which is simply not to echo the command. So a rule like

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 came across this line: void (*(*x)(void (*[10])(int *)))(int *) Can anybody tell me what it is? 回答1: To break this down yourself, start from the inner most parentheses and work your way out. (*[10]) (*[10])(int *) int as its argument (void (*[10])(int *)) int as its argument and returns void (*x)(void (*[10])(int *)) x is a pointer to a function which has as an argument (an array of 10 pointers to functions which has a pointer to int as its argument and returns void ) ..... I stopped partway through, but hopefully that helps. 回答2: cdecl is

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 was reading this page http://dev.mysql.com/doc/refman/5.0/en/mysql-fetch-row.html there is one line printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL"); from code MYSQL_ROW row; unsigned int num_fields; unsigned int i; num_fields = mysql_num_fields(result); while ((row = mysql_fetch_row(result))) { unsigned long *lengths; lengths = mysql_fetch_lengths(result); for(i = 0; i < num_fields; i++) { printf("[%.*s] ", (int) lengths[i], row[i] ? row[i] : "NULL"); } printf("\n"); } what does [%.*s] mean in that code ? 回答1: [%.*s] is a

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 took an example from an online website and the CSS contained a URL pointing to a png and some random letters in both cases can any one tell me how to make such codes or rather what those codes are about ... here is the html <center><input class="textbox"type="text" placeholder="E-mail"></center> here is the css .textbox { background: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABgAAAAYCAYAAADgdz34AAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAyBpVFh0WE1MOmNvbS5hZG9iZS54bXAAAAAAADw/eHBhY2tldCBiZWdpbj0i77u

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 converting some R code to Rcpp code and need to calculate the likelihood for a vector of observations given a vector of means and vector of standard deviations. If I assume the means are 0 and the standard deviations 1, I can write this function (running this requires the 'inline' and 'Rcpp' packages to be loaded), dtest1 = cxxfunction(signature( x = "numeric"), 'Rcpp::NumericVector xx(x); return::wrap(dnorm(xx, 0.0, 1.0));', plugin='Rcpp') and the result is as expected. > dtest1(1:3) [1] 0.241970725 0.053990967 0.004431848 However, if

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 got a nested list, named mylist which has length 4. Each element of this list is an experiment: exp1.1 , exp1.2 , exp2.1 and exp2.2 . Each experiment contains observations of length (in days) of four plant growth stages: EM-V6 V6-R0 R0-R4 and R4-R9 . Each growth stage is organized as a data frame with year and mean . Here is the complete data: mylist=structure(list(exp1.1 = structure(list(`EM-V6` = structure(list( year = 2011:2100, mean = c(34, 34, 32, 28, 25, 32, 32, 28, 27, 30, 32, 31, 33, 28, 26, 31, 33, 27, 34, 26, 28, 27, 27, 30, 29,

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: See: https://tools.ietf.org/html/rfc3986#section-3 And: https://tools.ietf.org/html/rfc3986#section-3.3 The origin of "abempty" is mysterious to me, and a quick search didn't turn up any definitions of it. 回答1: "abempty", as it states in the comments to the right of its usage in the rfc you reference, means that its value can be either an ab solute path or empty so ( abempty ). 回答2: “A path is always defined for a URI” (Section 3.3). “Abempty”, meaning away from However, when the authority is zero length and the path is empty, there is no

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've seen this in some answers on S/O where the point is made that the programming language doesn't matter as much for a crawler and so C++ is overkill vs say Python. Can someone please explain this in layman's terms so that there's no ambiguity about what is implied? Clarification of the underlying assumption here is also appreciated. Thanks 回答1: It means that I/O is the bottleneck here. The act of going out to the net to retrieve a page (I/O) is slower than analysing the page (CPU). So, making the CPU bit ten times faster will