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SQL Logic Operator Precedence: And and Or
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4 Answers
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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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What does this square bracket and parenthesis bracket notation mean [first1,last1)?
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4 Answers
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Numbering rows within groups in a data frame
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284
Use ave, ddply, dplyr or data.table:
df$num <- ave(df$val, df$cat, FUN = seq_along)
or:
l...
Custom numeric format string to always display the sign
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edited May 24 '16 at 21:50
Craig
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a...
Why does Math.round(0.49999999999999994) return 1?
...Java 7 no longer mandates this broken implementation.3
The problem
0.5+0.49999999999999994 is exactly 1 in double precision:
static void print(double d) {
System.out.printf("%016x\n", Double.doubleToLongBits(d));
}
public static void main(String args[]) {
double a = 0.5;
double b = 0...
How to configure PostgreSQL to accept all incoming connections
...this be configured in the pg_hba.conf file? I'm using postgreSQL version 8.4.
5 Answers
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Why `null >= 0 && null
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Michael Liquori
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answered May 26 '10 at 6:39
Christian C. SalvadóChristian C. Salv...
Clojure 1.2.1/1.3/1.4 'proxy generated in Grails 2.0.0 runtime fails. 1.2.0 is fine
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I found an Issue called CLJ-944 on clojure.org. There you can find a fix for ClassCastException:...
Performance of foreach, array_map with lambda and array_map with static function
... 1M numbers across a dozen attempts:
Foreach: 0.7 sec
Map on closure: 3.4 sec
Map on function name: 1.2 sec.
Supposing the lackluster speed of the map on closure was caused by the closure possibly being evaluated each time, I also tested like this:
function useMapClosure($numbers) {
$closu...