大约有 43,124 项符合查询结果（耗时：0.0473秒） [XML]
Creating an R dataframe row-by-row
...code in R.
If you can, allocate your entire data.frame up front:
N <- 1e4 # total number of rows to preallocate--possibly an overestimate
DF <- data.frame(num=rep(NA, N), txt=rep("", N), # as many cols as you need
stringsAsFactors=FALSE) # you don't know levels y...
Linux command (like cat) to read a specified quantity of characters
...
194
head works too:
head -c 100 file # returns the first 100 bytes in the file
..will extract ...
How do I check that a number is float or integer?
...
1
2
Next
1283
...
Guards vs. if-then-else vs. cases in Haskell
...
122
From a technical standpoint, all three versions are equivalent.
That being said, my rule of t...
It is more efficient to use if-return-return or if-else-return?
...
201
Since the return statement terminates the execution of the current function, the two forms are e...
SortedList, SortedDictionary and Dictionary
...
102
When iterating over the elements in either of the two, the elements will be sorted. Not so wi...
How to comment out a block of Python code in Vim
...
13 Answers
13
Active
...
How to get the nth occurrence in a string?
...
11 Answers
11
Active
...
Batch file to delete files older than N days
...
1085
Enjoy:
forfiles -p "C:\what\ever" -s -m *.* -d <number of days> -c "cmd /c del @path"
...