for-loop

问题 So using the Matching Package (Link to package here) We can work through a modified GenMatch example. library(Matching) data(lalonde) #introduce an id vaiable lalonde$ID <- 1:length(lalonde$age) X = cbind(lalonde$age, lalonde$educ, lalonde$black, lalonde$hisp, lalonde$married, lalonde$nodegr, lalonde$u74, lalonde$u75, lalonde$re75, lalonde$re74) BalanceMat <- cbind(lalonde$age, lalonde$educ, lalonde$black, lalonde$hisp, lalonde$married, lalonde$nodegr, lalonde$u74, lalonde$u75, lalonde$re75,

问题 This question already has answers here : Java: Infinite Loop Convention [closed] (5 answers) Closed 5 years ago . Can someone explain what is the condition for this for loop? for(;;) { //do sth. } 回答1: It has no condition. It's an infinite loop. 回答2: If the test condition is empty (and it is here), there is no test and the loop continues indefinitely. It's a short form for an infinite loop. 回答3: It is an infinite loop as the condition is empty. From the java specs If the Expression is not

问题 I just made the switch to linux and I am trying to write my first bash script. I have a folder that contains numerous folders, all with subfolders containing files. Something like: MainFolder Folder1 Sub1 (Contains many files) Sub2 (Contains many files) Folder2 Sub1 (Contains many files) Sub2 (Contains many files) . . . I want to move all the files contained in the sub-folders to the their parent folders. My first instinct is to try and write a for-loop. I was able to do one folder at a time

问题 I just made the switch to linux and I am trying to write my first bash script. I have a folder that contains numerous folders, all with subfolders containing files. Something like: MainFolder Folder1 Sub1 (Contains many files) Sub2 (Contains many files) Folder2 Sub1 (Contains many files) Sub2 (Contains many files) . . . I want to move all the files contained in the sub-folders to the their parent folders. My first instinct is to try and write a for-loop. I was able to do one folder at a time

问题 Im doing a back of the book exercise in Python Programming: An Intro to Comp Sci: for i in [1,3,5,7,9]: print(i, ":", i**3) print(i) this prints out 1:1 3:27 5:125 7:343 9:729 9 My questions is why does it print the extra 9? Wouldn't the last loop print be 9:729 ? It has to be something to do with the print(i, ":", i**3) because if I just put in: for i in [1,3,5,7,9]: print(i) It just prints 1 3 5 7 9 Thanks in advance as I have nobody else to help me! :) 回答1: In python for loops, the "body"

问题 I found that there is a difference between for loop and for-in loop in javascript. When I define a new array: var a=new Array(); Then I put some value into in but not contiguously for example: a[0]=0;a[1]=1;a[4]=4; When I use for(i=0;i<5;i++) to get the value and use alert to show it, it's different from using for(i in a) . The previous one will show elements in index 2,3 which shows "undefined" while for-in will show only index 0,1,and 4. Can anybody tell me why? 回答1: for (... in ...) is

问题 I'm having a problem using an unsigned char as an iterator. Using the following code results in being stuck inside a FOR loop. The output looks like this. unsigned char i; char * arr; int * freq; arr = (char *)(malloc(256*sizeof(char))); freq = (int *)(malloc(256*sizeof(int))); for (i=0; i<=255;i++){ arr[i]=i; freq[i]=0; printf("%c",i); } My question is why this happens? Is it due to using an unsigned char as an iterator? 回答1: i <= 255 If i is of type unsigned char and that type is 8 bit on

问题 I would like to run a KW-test over certain numerical variables from a data frame, using one grouping variable. I'd prefer to do this in a loop, instead of typing out all the tests, as they are many variables (more than in the example below). Simulated data: library(dplyr) set.seed(123) Data <- tbl_df( data.frame( muttype = as.factor(rep(c("missense", "frameshift", "nonsense"), each = 80)), ados.tsc = runif(240, 0, 10), ados.sa = runif(240, 0, 10), ados.rrb = runif(240, 0, 10)) ) %>% group_by

问题 I see this in a lot of game engine code. Is this supposed to be faster than if you were to declare it in the for loop body? Also this is followed by many other for loops, each of them using the same variable. int i; for(i=0; i<count; ++i) { } vs for(int i=0; i<count; ++i) { } Btw I never do this myself, just curious about the idea behind it, since apart from performance I don't know why anyone would do this. 回答1: The first way is probably the C way, the OLD OLD C way, where the second version

问题 I have been reading Object-Oriented Javascript by Stoyan Stefanov, and at one point he writes: The for-in loop is used to iterate over the element of an array (or an object, as we'll see later). This is it's only use; it can not be used as a general-purpose repetition mechanism that replaces for or while . Let's see an example of using a for-in to loop through the elements of an array. But bear in mind that this is for informational purposes only, as for-in is mostly suitable for objects, and