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Subset of rows containing NA (missing) values in a chosen column of a data frame
...olumn (in the example it would be column Var2) has there an 'NA' character string (I will replace it with your second statement), then I would like to choose the entire row to be part of the new data frame.
– John
Nov 2 '11 at 14:29
...
Should I use static_cast or reinterpret_cast when casting a void* to whatever
...g between pointer types (as is fairly common when indexing in memory via a char*, for example), static_cast will generate a compiler error and you'll be forced to use reinterpret_cast anyway.
In practice I use reinterpret_cast because it's more descriptive of the intent of the cast operation. You c...
How to obtain the start time and end time of a day?
...teTime zdtStop = today.plusDays( 1 ).atStartOfDay( zoneId ) ;
zdtStart.toString() = 2020-01-30T00:00+01:00[Africa/Tunis]
zdtStop.toString() = 2020-01-31T00:00+01:00[Africa/Tunis]
See the same moments in UTC.
Instant start = zdtStart.toInstant() ;
Instant stop = zdtStop.toInstant() ;
start.toS...
How can I check if an ip is in a network in Python?
...lt;<n-1) - 1
def dottedQuadToNum(ip):
"convert decimal dotted quad string to long integer"
return struct.unpack('L',socket.inet_aton(ip))[0]
def networkMask(ip,bits):
"Convert a network address to a long integer"
return dottedQuadToNum(ip) & makeMask(bits)
def addressInNet...
How do you run a SQL Server query from PowerShell?
...here is the function that I use:
function Invoke-SQL {
param(
[string] $dataSource = ".\SQLEXPRESS",
[string] $database = "MasterData",
[string] $sqlCommand = $(throw "Please specify a query.")
)
$connectionString = "Data Source=$dataSource; " +
"In...
Which @NotNull Java annotation should I use?
...get({FIELD, METHOD, PARAMETER, LOCAL_VARIABLE})
public @interface NotNull {String value() default "";}
package javax.annotation;
@TypeQualifier
@Retention(RUNTIME)
public @interface Nonnull {
When when() default When.ALWAYS;
static class Checker implements TypeQualifierValidator<Nonnu...
Haskell Type vs Data Constructor
...e to you.
Intermission
If you'd want to construct a binary tree to store Strings, you could imagine doing something like
data SBTree = Leaf String
| Branch String SBTree SBTree
What we see here is a type SBTree that contains two data constructors. In other words, there are two funct...
“Items collection must be empty before using ItemsSource.”
...ou caught the error yet? -->
</ItemsControl>
The bug? The extra > after the initial opening <ItemsControl> tag! The < got applied to the built-in Items collection. When the DataContext was later set, instant crashola. So look out for more than just errors surround you...
How to loop through all enum values in C#? [duplicate]
...
static void Main(string[] args)
{
foreach (int value in Enum.GetValues(typeof(DaysOfWeek)))
{
Console.WriteLine(((DaysOfWeek)value).ToString());
}
foreach (string value in Enum.GetNames(typeof(DaysOfWeek)))
{
...
Reflecting parameter name: abuse of C# lambda expressions or syntax brilliance?
...ple
C#:
public class Class1
{
public static void Foo(Func<object, string> f)
{
Console.WriteLine(f.Method.GetParameters()[0].Name);
}
}
F#:
Class1.Foo(fun yadda -> "hello")
Result:
"arg" is printed (not "yadda").
As a result, library designers should either avoi...