how to delete the temp file and cache files in ubuntu? where as in windows o/s we have cmd prompt to view the %temp% cmd to delete it? so kindly make the which cmd to use this option
I need to do a lot of cleaning in my Virtual Machine whose Operating System is Ubuntu.  Normally in Windows, there is this kind of directory that contain temporary files and that should be cleaned :  C:\Documents and Settings\Administrator\Local Settings\Temp   Does it exist such a directory in Ubuntu? If yes, what is it?  Thank you a lot.
Example of a series! Give an example of a convergent series $$\sum_{n=1}^{\infty}a_n$$ such that the series $$\sum_{n=1}^{\infty}a_{3n}$$ is divergent..  I cannot find find any kind of series... I am also be very thankful if you find a divergent series (changing the term convergent)... When I loaded the review page (in Stack Overflow, though I have no specific reason to think it is related) I got a weird hat in the upper left hand corner.    See the hat in the upper left hand corner?  That's belonging to user # .  His profile page also has the hat in a ... weird ... location, but not this weird.    I'm guessing this is due to the not-loaded image for the avatar (adblock blocks Facebook avatars for me often)?  It also causes the toolbar notification to show his link unless I'm hovering over something else.  It also changes the location of the gray box to the upper left hand corner when I hover over the hat (and hovering over the white box does nothing).  It's definitely him (or any not-loaded avatar perhaps), once he fell off the last 6 reviewers it stopped appearing. How to plot the first n rows of a table using pgfplots? When using pgfplots, is there a way to plot only the first n rows of a given table ?  Considering the following MWE file:  \documentclass[tikz]{standalone}  \usepackage{tikz} \usepackage{pgfplots} \pgfplotsset{compat=newest} \usepackage{amsmath}  \begin{document}      \begin{tikzpicture}         \begin{axis}[%             width=16cm,height=8cm,             view={-45}{65},             scale only axis,             xmin=200,xmax=500,             xlabel={data1},             ymin=0,ymax=100,             ylabel={data2},             zmin=0,zmax=1,             zlabel={data3},         ]         \addplot3 [             thick,smooth,             color= darkgray,             solid]             table[row sep=crcr] {                 250 0 0\\                 250 25 0.2\\                 250 50 0.3\\                 250 75 0.2\\                 250 100 0\\             };          \addplot3 [             thick,smooth,             color= darkgray,             solid]             table[row sep=crcr] {                 450 0 0.5\\                 450 25 0.1\\                 450 50 0\\                 450 75 0.1\\                 450 100 0.5\\             };         \end{axis}     \end{tikzpicture}% \end{document}   How can I plot only the first n=4 rows of each table and ask pgfplots to stop reading the table once this row is reached ?  Of course, for the above example, this seems useless, but when huge data tables are used, this could be extremely usefull, in particular to use the same data and focus on different parts of the table in different figures. Random weighted choice Consider the class below that represents a Broker:  public class Broker {     public string Name = string.Empty;     public int Weight = 0;      public Broker(string n, int w)     {         this.Name = n;         this.Weight = w;     } }   I'd like to randomly select a Broker from an array, taking into account their weights.  What do you think of the code below?  class Program     {         private static Random _rnd = new Random();          public static Broker GetBroker(List&lt;Broker&gt; brokers, int totalWeight)         {             // totalWeight is the sum of all brokers' weight              int randomNumber = _rnd.Next(0, totalWeight);              Broker selectedBroker = null;             foreach (Broker broker in brokers)             {                 if (randomNumber &lt;= broker.Weight)                 {                     selectedBroker = broker;                     break;                 }                  randomNumber = randomNumber - broker.Weight;             }              return selectedBroker;         }           static void Main(string[] args)         {             List&lt;Broker&gt; brokers = new List&lt;Broker&gt;();             brokers.Add(new Broker("A", 10));             brokers.Add(new Broker("B", 20));             brokers.Add(new Broker("C", 20));             brokers.Add(new Broker("D", 10));              // total the weigth             int totalWeight = 0;             foreach (Broker broker in brokers)             {                 totalWeight += broker.Weight;             }              while (true)             {                 Dictionary&lt;string, int&gt; result = new Dictionary&lt;string, int&gt;();                  Broker selectedBroker = null;                  for (int i = 0; i &lt; 1000; i++)                 {                     selectedBroker = GetBroker(brokers, totalWeight);                     if (selectedBroker != null)                     {                         if (result.ContainsKey(selectedBroker.Name))                         {                             result[selectedBroker.Name] = result[selectedBroker.Name] + 1;                         }                         else                         {                             result.Add(selectedBroker.Name, 1);                         }                     }                 }                   Console.WriteLine("A\t\t" + result["A"]);                 Console.WriteLine("B\t\t" + result["B"]);                 Console.WriteLine("C\t\t" + result["C"]);                 Console.WriteLine("D\t\t" + result["D"]);                  result.Clear();                 Console.WriteLine();                 Console.ReadLine();             }         }     }   I'm not so confident. When I run this, Broker A always gets more hits than Broker D, and they have the same weight.  Is there a more accurate algorithm?  Thanks! Why cofinality is a cardinal. Accessing raster attribute table in QGIS? I have some Python code that makes Raster Attribute Tables for GeoTiffs using GDAL.    In ArcGIS I can see these attribute tables fine and they behave how I like (as classifications) but in QGIS the whole concept of an attribute table seems to be missing.    Is there any way to access a RAT in QGIS? Truncated 200GB table but disk space not released I have only 2GB left, so I need to remove this history table. This table now is empty but the database disk space not released. And the database file is 320GB. regex error - nothing to repeat Find splitting field of $x^5-4x+2$ over $\mathbb{Q}$ I know how to get the splitting field from the roots but I just can't come up with any factorisation that gives me roots. Any suggestions? SELECT DISTINCT on multiple columns Supposing we have a table with four columns (a,b,c,d) of the same data type.  Is it possible to select all distinct values within the data in the columns and return them as a single column or do I have to create a function to achieve this? "A number of students" vs. "the number of students" Possible Duplicate:          From the grammatical view both are correct, but please explain the difference in meaning:   The number of students in the class is fifteen. A number of students were late for class. Why doesn't ZIP Compression compress anything? A 398MB directory was only compressed to 393MB using 7Z and Normal ZIP compression. Is this normal? If so, why do people continue to use ZIP on Windows? Flagging accepted "answers" It is common to see things described as the &quot;gold standard&quot;. It means that something is the best and is the ideal against which other things are to be compared; it cannot be superseded. I often , where a certain diagnostic test (e.g., the nasopharyngeal swab PCR test for infection with the Coronavirus causing COVID-19) is considered the most accurate and then other tests (e.g., cheaper or faster tests) are then evaluated against this benchmark. The etymology is covered in . In short, it is derived from the . Thus gold was the thing against which the value of all other currencies was measured. I don't like this term and would like to avoid using it. First, the desired meaning is not predominant; if you  you will mostly get results for the monetary system, not the more general phrase. Second, the etymology is outdated; the original meaning of the term now has the opposite connotation. The monetary gold standard was abandoned in the 1970s. Economists consider the gold standard to be a bad monetary system. Thus, if you are interested in economics and history, the term &quot;gold standard&quot; actually is associated with being outdated and flawed -- which is close to the opposite of the intended meaning. (Of course, many people are unaware of the original meaning of the term. ) (A note in response to comments: Why I want to avoid this term is relevant, but not essential, to the question. If you don't see a problem with the term, the question can be answered regardless.) My question: Is there a better phrase to use in place of &quot;gold standard&quot;? For example, what term could be used in a medical study comparing a new diagnostic test against the gold standard test? I'm not aware of any good substitute that has essentially the same meaning. Here are two example sentences where I would like a replacement:   A nasal swab is the gold standard for diagnosing COVID-19.     The  served as the gold standard for all scales from 1889 until 2019.   The best substitute I can think of is &quot;official,&quot; as in &quot;a nasal swab is the official way to diagnose COVID-19&quot;. &quot;Official&quot; implies some form of uniqueness. But &quot;official&quot; implies the existence of some authority that gives it this designation (as opposed to scientific consensus). A  asks for a &quot;perhaps humorous&quot; alternative -- the suggestion there, &quot;mother of all&quot;, is not appropriate here. (There is also .)  In response to the answers and comments doubting the premise of this question: I personally have a negative association with the phrase &quot;gold standard&quot; because I know people who advocate for returning to the gold standard or its modern equivalent, , and have discussed the topic at length. Several  US  continue to advocate for a return to the gold standard. Thus asserting that no one will interpret the phrase in terms of monetary policy is simply not convincing. Synaptics driver doesn't load sometimes Unknown Syntax Error in Code So, I am following a , and it is using Python code to create an audio visualizer in Blender. Now, I've always been a coding geek, but I don't actually know Python. I've taken a few shots at it but overall, I don't know Python, however, I can read and understand the code because I know basic programming concepts. Now, I'm following this tutorial as closely as I can (the tutorial does not provide code to copy and paste) and I am getting a syntax error. As far as I can tell, there is no syntax error. The line of code (specified by the error message) appears perfect. This line of code is supposed to set the 3D cursor to the active object's origin. Here's the catch: if I run that exact same line of code in the console, it executes just fine. So here's the error message I get:  File "C:\Me\Blender\Blender Projects\audio visualisation.blend\AudioVisualizer", line 17 bpy.context.scene.cursor_location = bpy.context.active_object.location    ^ SyntaxError: invalid syntax location: &lt;unknown location&gt;:-1   It tells me to look in the console for error message, but the console doesn't output anything.    Thanks!  EDIT: Alright. I've tried all the examples and all the procedures that have been suggested by you guys, but it keeps feeding me errors. According to the console, one of the problems it is spitting out is in C:\Program Files\Blender Foundation\Blender\2.74\scripts\modules\bpy\ops.py. This makes me think there is a bug in the API that is causing one of the many errors. EDIT: Here are the error messages I get for my code. Original Code:  Error:   File "C:\Gannon\Blender\Blender Projects\audio visualisation.blend\Audi o Visualizer", line 35     bpy.ops.graph.sound_bake(filepath="C:\Gannon\Blender\Sounds\Music\Batty McFa dden.mp3", low=i*step high=i*step+step                           ^ SyntaxError: invalid syntax    gandalf3's Code and zeffii's Code are essentially the same with alternative formatting which changes the line numbers where the error occurs.  Error: Unsupported audio format  Traceback (most recent call last):   File "C:\Gannon\Blender\Blender Projects\audio visualisation.blend\Audio Visua lizer", line 42, in &lt;module&gt;   File "C:\Gannon\Blender\Blender Projects\audio visualisation.blend\Audio Visua lizer", line 35, in spiral   File "C:\Program Files\Blender Foundation\Blender\2.74\scripts\modules\bpy\ops .py", line 189, in __call__     ret = op_call(self.idname_py(), None, kw) RuntimeError: Error: Unsupported audio format So far, I know the matrices $$S=\left( \begin{matrix} 0&amp;-1\\ 1&amp;0 \end{matrix} \right), \quad T=\left( \begin{matrix} 1&amp;1\\ 0&amp;1 \end{matrix} \right) $$ generate SL$(2,\mathbb{Z})$. $S^2=(ST)^3=-I$. I also know the matrices $$X=\left( \begin{matrix} 1&amp;1\\ 1&amp;2 \end{matrix} \right), \quad Y=\left( \begin{matrix} 2&amp;1\\ 1&amp;1 \end{matrix} \right) $$ with their inverses $X^{-1},Y^{-1}$ generate SL$(2,\mathbb{Z})'$, the commutator subgroup. I'm interested in what the quotient $SL(2,\mathbb{Z})/SL(2,\mathbb{Z})'$ is. In general, how would I go about computing the quotient of two matrix groups? I'm trying to use GAP but I'm having a lot of trouble! Motivation behind the definition of ideal class group What does it mean if a Python object is "subscriptable" or not? Which types of objects fall into the domain of "subscriptable"? Non-existence of a bijective analytic function between annulus and punctured disk