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Find MongoDB records where array field is not empty
... To me that's the correct approach, since it makes sure the array exists and is not empty.
– LeandroCR
Mar 19 '15 at 14:34
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Regex to validate date format dd/mm/yyyy
...2-9]\d)?\d{2})$
I tested it a bit in the link Arun provided in his answer and also here and it seems to work.
Edit February 14th 2019: I've removed a comma that was in the regex which allowed dates like 29-0,-11
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Is MATLAB OOP slow or am I doing something wrong?
...menting with MATLAB OOP , as a start I mimicked my C++'s Logger classes and I'm putting all my string helper functions in a String class, thinking it would be great to be able to do things like a + b , a == b , a.find( b ) instead
of strcat( a b ) , strcmp( a, b ) , retrieve first element o...
How do you know what to test when writing unit tests? [closed]
... code, or a completely new feature.
Start simple. Don’t go running off and trying to get your head round
a testing framework as well as being
TDD-esque. Debug.Assert works fine.
Use it as a starting point. It doesn’t
mess with your project or create
dependencies.
Start positive. Yo...
Why does changing 0.1f to 0 slow down performance by 10x?
... than on normalized floating-point. This is because many processors can't handle them directly and must trap and resolve them using microcode.
If you print out the numbers after 10,000 iterations, you will see that they have converged to different values depending on whether 0 or 0.1 is used.
Here...
Normalize data in pandas
Suppose I have a pandas data frame df :
5 Answers
5
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Aligning text and image on UIButton with imageEdgeInsets and titleEdgeInsets
...ines of text such that there's about 2-3 pixels of space between the image and the start of text. The control itself is Center aligned horizontally (set through Interface Builder)
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Adding a column to a data.frame
...xt, [[.data.frame.
Data frames can be indexed in several modes. When [ and [[ are used with a single vector index (x[i] or x[[i]]), they index the data frame as if it were a list.
my.dataframe["new.col"] <- a.vector
my.dataframe[["new.col"]] <- a.vector
The data.frame method for $, ...
What's the fastest way to merge/join data.frames in R?
...he first. If there are duplicates in the second data frame then the match and merge approaches are not the same. Match is, of course, faster since it is not doing as much. In particular it never looks for duplicate keys. (continued after code)
DF1 = data.frame(a = c(1, 1, 2, 2), b = 1:4)
DF2 = da...
What's the difference between a single precision and double precision floating point operation?
What is the difference between a single precision floating point operation and double precision floating operation?
11 Answ...