Use `rle()`:

    y &lt;- rle(c(1,0,0,0,1,0,0,0,0,0,2,0,0))
    y$lengths[y$values==0]



This can be done in an efficient way by using indexes of where the values change:

    x &lt;- c(1,0,0,0,1,2,1,0,0,1,1)

Find where the values change:

    diffs &lt;- x[-1L] != x[-length(x)]

Get the indexes, and then get the difference in subsequent indexes:

    idx &lt;- c(which(diffs), length(x))
    diff(c(0, idx))

**Background**

I have a Windows service that uses various third-party DLLs to perform work on PDF files.  These operations can use quite a bit of system resources, and occasionally seem to suffer from memory leaks when errors occur.  The DLLs are managed wrappers around other unmanaged DLLs.

**Current Solution**

I&#39;m already mitigating this issue in one case by wrapping a call to one of the DLLs in a dedicated console app and calling that app via Process.Start().  If the operation fails and there are memory leaks or unreleased file handles, it doesn&#39;t really matter.  The process will end and the OS will recover the handles.

I&#39;d like to apply this same logic to the other places in my app that use these DLLs.  However, I&#39;m not terribly excited about adding more console projects to my solution, and writing even more boiler-plate code that calls Process.Start() and parses the output of the console apps.

**New Solution**

An elegant alternative to dedicated console apps and Process.Start() seems to be the use of AppDomains, like this:  &lt;http://blogs.geekdojo.net/richard/archive/2003/12/10/428.aspx&gt;.

I&#39;ve implemented similar code in my application, but the unit tests have not been promising.  I create a FileStream to a test file in a separate AppDomain, but don&#39;t dispose it.  I then attempt to create another FileStream in the main domain, and it fails due to the unreleased file lock.

Interestingly, adding an empty DomainUnload event to the worker domain makes the unit test pass.  Regardless, I&#39;m concerned that maybe creating &quot;worker&quot; AppDomains won&#39;t solve my problem.

Thoughts?

**The Code**

    /// &lt;summary&gt;
    /// Executes a method in a separate AppDomain.  This should serve as a simple replacement
    /// of running code in a separate process via a console app.
    /// &lt;/summary&gt;
    public T RunInAppDomain&lt;T&gt;( Func&lt;T&gt; func )
    {
    	AppDomain domain = AppDomain.CreateDomain ( &quot;Delegate Executor &quot; + func.GetHashCode (), null,
    		new AppDomainSetup { ApplicationBase = Environment.CurrentDirectory } );
    		
    	domain.DomainUnload += ( sender, e ) =&gt;
    	{
    		// this empty event handler fixes the unit test, but I don&#39;t know why
    	};
    
    	try
    	{
    		domain.DoCallBack ( new AppDomainDelegateWrapper ( domain, func ).Invoke );
    
    		return (T)domain.GetData ( &quot;result&quot; );
    	}
    	finally
    	{
    		AppDomain.Unload ( domain );
    	}
    }
    
    public void RunInAppDomain( Action func )
    {
    	RunInAppDomain ( () =&gt; { func (); return 0; } );
    }

    /// &lt;summary&gt;
    /// Provides a serializable wrapper around a delegate.
    /// &lt;/summary&gt;
    [Serializable]
    private class AppDomainDelegateWrapper : MarshalByRefObject
    {
    	private readonly AppDomain _domain;
    	private readonly Delegate _delegate;
    
    	public AppDomainDelegateWrapper( AppDomain domain, Delegate func )
    	{
    		_domain = domain;
    		_delegate = func;
    	}
    
    	public void Invoke()
    	{
    		_domain.SetData ( &quot;result&quot;, _delegate.DynamicInvoke () );
    	}
    }

**The unit test**

    [Test]
    public void RunInAppDomainCleanupCheck()
    {
    	const string path = @&quot;../../Output/appdomain-hanging-file.txt&quot;;
    
    	using( var file = File.CreateText ( path ) )
    	{
    		file.WriteLine( &quot;test&quot; );
    	}
    
    	// verify that file handles that aren&#39;t closed in an AppDomain-wrapped call are cleaned up after the call returns
    	Portal.ProcessService.RunInAppDomain ( () =&gt;
    	{
    		// open a test file, but don&#39;t release it.  The handle should be released when the AppDomain is unloaded
    		new FileStream ( path, FileMode.Open, FileAccess.ReadWrite, FileShare.None );
    	} );
    
    	// sleeping for a while doesn&#39;t make a difference
    	//Thread.Sleep ( 10000 );
    
    	// creating a new FileStream will fail if the DomainUnload event is not bound
    	using( var file = new FileStream ( path, FileMode.Open, FileAccess.ReadWrite, FileShare.None ) )
    	{
    	}
    }

Replacing Process.Start with AppDomains

I am often comparing data in tables in different databases.  These databases do **not** have the same schema.  In TSQL, I can reference them with the  `DB&gt;user&gt;table` structure (`DB1.dbo.Stores`, `DB2.dbo.OtherPlaces`) to pull the data for comparison.  I like the idea of LINQPad quite a bit, but I just can&#39;t seem to easily pull data from two different data contexts within the same set of statements.

I&#39;ve seen people suggest simply changing the connection string to pull the data from the other source into the current schema but, as I mentioned, this will not do.  Did I just skip a page in the FAQ?  This seems a fairly routine procedure to be unavailable to me.

In the &quot;easy&quot; world, I&#39;d love to be able to simply reference the typed datacontext that LINQPad creates.  Then I could simply:

```csharp
DB1DataContext db1 = new DB1DataContext();
```

```csharp
DB2DataContext db2 = new DB2DataContext();
```

And work from there.

LINQPad, using multiple datacontexts

In R, what would be the most efficient/simplest way to count runs of identical elements in a sequence?

For example, how to count the numbers of consecutive zeros in a sequence of non-negative integers:

    x &lt;- c(1,0,0,0,1,0,0,0,0,0,2,0,0) # should give 3,5,2


How can I count runs in a sequence?

In R, what would be the most efficient/simplest way to count runs of identical elements in a sequence?
For example, how to count the numbers of consecutive zeros in a sequence of non-negative integers:
<pre><code class="hljs language-r">x &#x3C;- c(1,0,0,0,1,0,0,0,0,0,2,0,0) # should give 3,5,2
</code></pre>

I have a csv file where some of the numerical values are expressed as strings with commas as thousand separator, e.g. `&quot;1,513&quot;` instead of `1513`. What is the simplest way to read the data into R?

I can use `read.csv(..., colClasses=&quot;character&quot;)`, but then I have to strip out the commas from the relevant elements before converting those columns to numeric, and I can&#39;t find a neat way to do that.

How to read data when some numbers contain commas as thousand separator?

Is there a certain R-gotcha that had you really surprised one day? I think we&#39;d all gain from sharing these.

Here&#39;s mine: in list indexing, `my.list[[1]]` is not `my.list[1]`. Learned this in the early days of R.

What&#39;s the biggest R-gotcha you&#39;ve run across?

Say I have a bunch of functions, each with something like`MyFunction.1`, etc.  I want to pass these functions into another function, which prints out a small report.  Ideally I&#39;d like to be able to label sections of a report by which function is being used to generate the results.  

So are there any nice ways of getting the name of a predefined function as a string?

Getting a function name as a string

I have a vector x, that I would like to sort based on the order of values in vector y. The two vectors are not of the same length.

    x &lt;- c(2, 2, 3, 4, 1, 4, 4, 3, 3)
    y &lt;- c(4, 2, 1, 3)

The expected result would be:

    [1] 4 4 4 2 2 1 3 3 3

How do I sort one vector based on values of another

I&#39;m outputting a dataframe to html via `xtable`. I want to add commas to numbers in a couple columns of the table. I figured before I did my own paste hack I&#39;d check if there is a built in way to do this.

add commas into number for output

I need to work with large files and must find differences between two. And I don&#39;t need the different bits, but the number of differences.

To find the number of different rows I come up with 

    diff --suppress-common-lines --speed-large-files -y File1 File2 | wc -l

And it works, but is there a better way to do it?

And how to count the exact number of differences (with standard tools like bash, diff, awk, sed some old version of perl)?

How to count differences between two files on linux?

Is there any way under linux/terminal to count, how many times the char f occurs in a plain text file?

Count occurrences of a char in plain text file

I have a vector &#39;y&#39; and I count the different values using `table`:

    y &lt;- c(0, 0, 1, 3, 4, 4)
    table(y)
    # y
    # 0 1 3 4 
    # 2 1 1 2 

However, I also want the result to include the fact that there are zero 2&#39;s and zero 5&#39;s. Can I use `table()` for this?

Desired result:

    # y
    # 0 1 2 3 4 5 
    # 2 1 0 1 2 0

Include levels of zero count in result of table()

Can someone recommend a function that can allow me to count and return the number of items in a list? 

```
library(stringr)

l &lt;- strsplit(words, &quot;a&quot;)

if(# number of items in list l &lt; 1) 
  next
```




R: Count number of objects in list

I&#39;ve notice that in Oracle, the query

    SELECT COUNT(*) FROM sometable;

is very slow for large tables.  It seems like the database it actually going through every row and incrementing a counter one at a time.  I would think that there would be a counter somewhere in the table how many rows that table has.

So if I want to check the number of rows in a table in Oracle, what is the fastest way to do that?

Content Type	Original Author	Original Content on Stackoverflow
Question	andrekos	View Question on Stackoverflow
Solution 1 - R	Rob Hyndman	View Answer on Stackoverflow
Solution 2 - R	Shane	View Answer on Stackoverflow

How can I count runs in a sequence?

R Problem Overview

R Solutions

Solution 1 - R

Solution 2 - R

LINQPad, using multiple datacontexts

Replacing Process.Start with AppDomains

Attributions