大约有 47,000 项符合查询结果（耗时：0.0439秒） [XML]
How to prevent ifelse() from turning Date objects into numeric objects
...<- "Date"
str(dates)
At first this felt a little "hackish" to me. But now I just think of it as a small price to pay for the performance returns that I get from ifelse(). Plus it's still a lot more concise than a loop.
...
How to implement the Android ActionBar back button?
...ress the back button. This should be done in the AndroidManifest.xml too.
Now you can enable the back button in the onCreate method of your "child" activity.
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getActionBar().setDisplayHomeAsUp...
Merging 2 branches together in GIT
... A
$ git checkout A
# hack hack
$ git commit -am "commit on branch A"
so now there are three separate branches (namely A B and C) with different heads
to get the changes from B and C back to A, checkout A (already done in this example) and then use the merge command:
# create an octopus merge
$ ...
Swift - class method which must be overridden by subclass
...
As of Swift 2.0 there are now protocol extensions too :) Apple Reference.
– Ephemera
Sep 13 '15 at 9:25
4
...
In Firebase, is there a way to get the number of children of a node without loading all the node dat
...way to count children without loading data, but we do plan to add it.
For now, one solution would be to maintain a counter of the number of children and update it every time you add a new child. You could use a transaction to count items, like in this code tracking upvodes:
var upvotesRef = new Fi...
Writing files in Node.js
... he wanted to save the file on /home directory I suggested to chmod it. I know it could generate a security issue. But well, if the user wants to save there, that's the solution. P.S: I agree with what you said (:
– Denys Vitali
Jan 29 '14 at 22:51
...
What is JSON and why would I use it?
...ipt object you must first parse it, var x = JSON.parse('{"x":"y"}');, x is now an object but this is not JSON anymore.
See Javascript object Vs JSON
When working with JSON and JavaScript, you may be tempted to use the eval function to evaluate the result returned in the callback, but this is not...
SQL multiple column ordering
...en performs STABLE sorting by column1. This is more clear for people that knows what stable sorting is.
– Atom
Oct 3 '16 at 13:49
...
How to define a two-dimensional array?
...w, h = 8, 5;
Matrix = [[0 for x in range(w)] for y in range(h)]
You can now add items to the list:
Matrix[0][0] = 1
Matrix[6][0] = 3 # error! range...
Matrix[0][6] = 3 # valid
Note that the matrix is "y" address major, in other words, the "y index" comes before the "x index".
print Matrix[0]...
Pandas get topmost n records within each group
...
Yes, I think that's it. Overlooked this somehow. Do you know good way to number records within group?
– Roman Pekar
Nov 19 '13 at 10:48
...