I had a folder /acme, that contained data.  I found out that I was supposed to have already mounted /dev/centos/lv_acme to /acme.  I did a minimum amount of research on the web, and it appeared that mounting did not erase data.  (Though I now assume I misunderstood what I read.)    I executed the command  mount /dev/centos/lv_acme /acme     As I'm sure you've figured by now, /acme no longer contains my data.  Is there any way of recovering the data that was in /acme?
On my headless NAS I have sdf1 (a flash-card) mounted as / while /home is mounted from lv00 (an LVM volume backed by a software RAID). To be able to access the machine when the RAID fails, I have a copy of my ssh public key, etc. in /home/foo/.ssh on the file-system from sdf1. To update the files that are hidden by the mounted /home I normally remount lv00 in /mnt/home, do what I have to do, and then move lv00 back in place. Is there a way to achieve this without unmounting /home?
Regular cast vs. static_cast vs. dynamic_cast I'm having some difficulty understanding how to interpret variable importance output from the Random Forest package. Mean decrease in accuracy is usually described as "the decrease in model accuracy from permuting the values in each feature".   Is this a statement about the feature as a whole or about specific values within the feature? In either case, is the Mean Decrease in Accuracy the number or proportion of observations that are incorrectly classified by removing the feature (or values from the feature) in question from the model?   Say we have the following model:  require(randomForest) data(iris) set.seed(1) dat &lt;- iris dat$Species &lt;- factor(ifelse(dat$Species=='virginica','virginica','other')) model.rf &lt;- randomForest(Species~., dat, ntree=25, importance=TRUE, nodesize=5) model.rf varImpPlot(model.rf)     Call:  randomForest(formula = Species ~ ., data = dat, ntree = 25,  proximity = TRUE, importance = TRUE, nodesize = 5)  Type of random forest: classification Number of trees: 25 No. of variables tried at each split: 2          OOB estimate of  error rate: 3.33% Confusion matrix:           other virginica class.error other        97         3        0.03 virginica     2        48        0.04     In this model, the OOB rate is rather low (around 5%). Yet, the Mean Decrease in Accuracy for the predictor (Petal.Length) with the highest value in this measure is only around 8.   Does this mean that removing Petal.Length from the model would only result in an additional misclassification of 8 or so observations on average?   How could the Mean Decrease in Accuracy for Petal.Length be so low, given that it's the highest in this measure, and thus the other variables have even lower values on this measure? Incorrectly answered 'No' to "Any previous visa refusals..." on a UK Standard Visitor visa application. How can I fix my mistake? I'm from Lebanon and I've been working in Saudi Arabia for nine years. In 2012, I put the money that I collected from my job as a teacher in my father's Lebanese account since I didn't have one in Lebanon. During the interview, my interviewer told me that my application will be rejected because I don't have proof that this money is mine and clearance officer will think someone else gave me the money. I didn't know that I had to bring with me from Saudi Arabia an employment letter and bank statements to prove that this money is mine and I earned it by working in Saudi Arabia. Anyways, my visa did get refused as my interviewer had told me it would be.    Last May, I was granted a US visitor visa Multi Entry for 5 years. I wanted to visit the US in August for 10 days but my mom entered the hospital so I had to postpone it. Now I'm applying for a teacher training program in the UK. I received an invitation letter from Brighton University and so I applied for a UK Standard Visitor visa. After I paid and printed the application, I realized that I answered the question Any previous visa rejections ... with "NO" and I don't know how should I fix this.  Please note that I still didn't give my biometrics, I still didn't use my US visa which I received on May 2016, I paid for my application so I can't amend it online. I'm supposed to give my biometrics and submit my documents this Monday.  If I don't say anything will they check it and refuse me?    Will my US visa be an advantage and they will disregard the previous rejection or should I correct it when I submit my documents this Monday? Let A and B be sets. Show that A is a subset of B if and only if for any set C, one has A union C is a subset of B union C. Can you verify my proof if it is right?  Let $A$ and $B$ be sets.  (a) Show that $A$ is a subset of $B$ if and only if for any set $C$, one has $A$ union $C$ is a subset of $B$ union $C$. (b) Show that $A$ is a subset of $B$ if and only if for any set $C$, one has $A$ intersect $C$ is a subset of $B$ intersect $C$.  Edited Solution :  (a)  (=>) Given A is a subset of B, this implies A U B = B. Given a set C, A U B U C = B U C. Since A is a subset of B, this implies A U C is a subset of B U C.      Solution 1 :(&lt;=) Given A U C is a subset of B U C , For A U C , x is a member of A U C . For B U C, x is a member of B U C. Suppose x is a member of A but not a member of B, meaning A is not a subset of B. Therefore , A U C is not a subset of B U C. Hence, A must be a subset of B.      Solution 2 :(&lt;=) Given A U C is a subset of B U C, For A U C, x is a member of A U C and for B U C, x is a member of B U C. Suppose C is a disjoint set. Since A U C is a subset of B U C, it follows that A is a subset of B.  (b) (=>) Since A is a subset of B , it follows that A U B = B. [A intersect C] is a subset of A and  [B intersect C ] is a subset of B by definition of intersection. Let x be member of A and member of C. Since [ A intersect C ] is a subset of A, x must be in A. Let x be a member of B and member of C. Since [ B intersect C ] is a subset of B, x must be in B. Therefore, A intersect C is a subset of B intersect C.  (&lt;=) Since A intersect C is a subset of B intersect C, suppose we let Set C be a subset of B and a subset of A as well. C is a subset of A implies A intersect C is equals to C. C is a subset of B implies B intersect C is equals to C as well. Since A intersect C is equals to B intersect C, A is a subset of B. I think sometimes there is a need to post question as anonymous, reason being to avoid linking content of a question with the identity of the questioner. This may not be so evident or required on technical sites like stackoverflow.com but sometimes is a necessity on sites like  or maybe in future depression.stackexchange.com  On such sites user may not want to link his identity to some questions where he may detail about his being over-weight or skinny or maybe some other attribute which he may like to keep private and avoid making his concerns public, but still want to ask a question with valid data.  I am not suggesting that user asking question should not be registered or not responsible for content. I think all down-votes or up-votes should still be attributed to user, but this way most users would not suffer , and reputation could even be used for a bounty. The only change should be that while asking question a valid registered user can hide his identity (the whole user signature block/user card and the reputation should be replaced by "identity-hidden") and that question should not be listed in his public profile.  Anyway identity of questioner doesn't add much value to question. If we think such anonymous question may reduce social nature of Stack Exchange sites, and maybe majority of questions will become anonymous we can curb that by putting a daily or monthly limit per user or put a price of say 50 reputation per anonymous question.  PS: I don't think this is duplicate of        because motive for question and reason for feature request are different, and I propose a different solution too, because creating another account for asking such questions has many problems which having a single account doesn't have    I don't have to manage other account If I keep single account I still may want to keep my details to be linked to my non-anonymous questions I may want to use reputations I earned as bounty for anonymous questions    also allows anonymous questions and may be we can take some hint from there. When do relativistic effects need to be explicitly included? I'm new to latex, I'm thankful if someone can give me an example script to customize TOC that looks like  Chapter 1.XXXXXX                                                            (1-15)  1.1 Introduction 1.2 xxxxxxxx 1.3 xxxxxxxxxx 1.4 xxxxxxx ...............  Chapter 2.xxxxxxx  2.1 xxxxx ......                                                           (16-30)  because the (default) TOC appears to be very large for my book, since it arranges the section name row-by-row. Security of GCM if Implemented with Stream Cipher instead of Block Cipher How are qubits better than classical bit if they collapse to a classical state after measurement? Classical computers store information in bits, which can either be $0$ or $1$, but, in a quantum computer, the qubit can store $0$, $1$ or a state that is the superposition of these two states. Now, when we make a "measurement" (to determine the state of qubit), it changes the state of the qubit, collapsing it from its superposition of $0$ and $1$ to the specific state consistent with the measurement result.  If from a measurement of a qubit we obtain only a single bit of information ($0$ or $1$, because the qubit collapses to either of the states), then, how is a qubit better than a classical bit? Since ultimately we are only able to get either $0$ or $1$ from either classical or quantum bit.  If you can explain with an example, it may be helpful. How can I share an iCloud photo album? Line-breaking widget layout for Android I'm trying to create an activity that presents some data to the user. The data is such that it can be divided into 'words', each being a widget, and sequence of 'words' would form the data ('sentence'?), the ViewGroup widget containing the words. As space required for all 'words' in a 'sentence' would exceed the available horizontal space on the display, I would like to wrap these 'sentences' as you would a normal piece of text.  The following code:  public class WrapTest extends Activity {     /** Called when the activity is first created. */     @Override     public void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         LinearLayout l = new LinearLayout(this);         LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(                 LinearLayout.LayoutParams.FILL_PARENT,                 LinearLayout.LayoutParams.WRAP_CONTENT);         LinearLayout.LayoutParams mlp = new LinearLayout.LayoutParams(                 new ViewGroup.MarginLayoutParams(                         LinearLayout.LayoutParams.WRAP_CONTENT,                         LinearLayout.LayoutParams.WRAP_CONTENT));         mlp.setMargins(0, 0, 2, 0);          for (int i = 0; i &lt; 10; i++) {             TextView t = new TextView(this);             t.setText("Hello");             t.setBackgroundColor(Color.RED);             t.setSingleLine(true);             l.addView(t, mlp);         }          setContentView(l, lp);     } }   yields something like the left picture, but I would want a layout presenting the same widgets like in the right one.        Is there such a layout or combination of layouts and parameters, or do I have to implement my own ViewGroup for this? I have iterate over numbers in various order. I am able to display them in increasing order, even with steps like:  $ seq --separator="," 1 10 1,2,3,4,5,6,7,8,9,10 $ seq --separator="," 1 2 10 1,3,5,7,9   I am also able to display them in reverse order, neither continuous nor step wise.  $ seq --separator="," 10 1    $ seq --separator="," 10 2 1   No output for above commands.   My shell details:  $ bash --version GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu) Copyright (C) 2005 Free Software Foundation, Inc.   Let me know how I would be able to display the numbers in descending order? Alternative activity monitors for OS X? I’m a bit intrigued by the new detailed activity monitors and progress indicators in Windows 8 (copying files, the task monitor, network activity, etc.) It got me thinking: surely there must be some better alternatives to the built-in Activity Monitor.app?  “Better” as in more detailed and nicer graphs. Specifically, it would be interested and see percentage disk I/O (out of disk capacity), memory usage, and CPU usage in the same nice way   The Building windows blog has an article  in Windows 8.  I just think that OS X’s task manager — which I have always found superior — just doesn’t cut it anymore compared to what is coming in Windows 8. A question about causality and Quantum Field Theory from improper Lorentz transformation How do you handle aspect ratio differences with Unity 2D? I've gotten a lot of answers to this question, but they are all generic and generally not very useful.  None of the tutorials talk about aspect ratio and dealing with mobile devices and there are a zillion ways to do it, all seem to have gotcha's and flaws.  I really would love to know what successful games have used to handle different aspect ratios on iOS and Android without making a zillion different sized assets.  I am strictly speaking mobile, not desktop, specifically with Unity and I don't care about the UI, I only care about the gameplay canvas.  Issues I have in mind is when there are key things that have to be in certain places and cannot fall off the screen.  Using black bars on top or bottom is unacceptable these days. I know that Windows XP 32-bit can be configured, through , to support more than 3.5&nbsp;GB of RAM.  Is there a good tutorial to do this with Windows 7 32-bit?  As to why I don't simply use 64-bit Windows 7: The software for my Internet connection (cell phone-as-modem) will only work in 32-bit environments. PDF of a sum of exponential random variables Let $X_i$ for $i=1,2,...$ be a sequence of i.i.d exponential random variables with common parameter $\lambda$. Let $N$ be a geometric random variable with parameter $p$ that is independent of the sequence $X_i$. What is the pdf of the random variable $Y=\Sigma_{i=1}^N X_i$. How to Backup and Restore Android OS without Rooting What's the difference between $\equiv$ and $\leftrightarrow$ in a formal proof? I have recently created a logo. I have seen an online trend of showing off a logo in a realistic environment, illustrating possible use cases of the logo.  An example of this can be seen here, with the original logo at the bottom and a 3D mockup at the top:    How can I create such a mockup?