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Find MongoDB records where array field is not empty
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873
If you also have documents that don't have the key, you can use:
ME.find({ pictures: { $exists:...
How to convert floats to human-readable fractions?
Let's say we have 0.33 , we need to output 1/3 .
If we have 0.4 , we need to output 2/5 .
26 Answers
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Adding a column to a data.frame
...cording to column 1 ( h_no ) in that way that the first series of h_no 1,2,3,4 is class 1, the second series of h_no (1 to 7) is class 2 etc. such as indicated in the last column.
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Numbering rows within groups in a data frame
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answered Oct 16 '12 at 23:41
mnelmnel
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How to select rows with one or more nulls from a pandas DataFrame without listing columns explicitly
I have a dataframe with ~300K rows and ~40 columns.
I want to find out if any rows contain null values - and put these 'null'-rows into a separate dataframe so that I could explore them easily.
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Applying a function to every row of a table using dplyr?
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edited Aug 6 '19 at 3:20
answered Jul 14 '14 at 0:20
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Cannot ping AWS EC2 instance
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answered May 30 '15 at 9:39
RakibRakib
8,9821010 gold badges5555 silver badges9090 bronze badges
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List of lists changes reflected across sublists unexpectedly
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593
When you write [x]*3 you get, essentially, the list [x, x, x]. That is, a list with 3 references...
How to randomize (or permute) a dataframe rowwise and columnwise?
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234
Given the R data.frame:
> df1
a b c
1 1 1 0
2 1 0 0
3 0 1 0
4 0 0 0
Shuffle row-wise:
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