Why does a question appear as modified by the Community user, but when you click on it there's nothing in the question or its answers done by him/it ?
On the meta home page I noticed the  is listed as doing something, but cannot figure out what it is.  There is nothing on the  or its , but the recent activity is listed with the same timestamp.
Adding materials to more than one object Is it possible to add a texture or material to more than one object at a time? At college we use ArcGIS Desktop 10, but that does not function on my Mac so I have QGIS there instead.  I want to do my exercises with QGIS, but in ArcGIS Desktop we use .lyr files with ArcMap and .lyrx files with ArcGIS Pro, and they are not supported by QGIS.  Does anyone know, how I can connect the *.lyr files to my *.shp files to use them on my Mac with QGIS? I run below command on ubuntu 16.4 :  sudo add-apt-repository ppa:noobslab/apps  of below question:    and get below error:  Traceback (most recent call last):   File "/usr/bin/add-apt-repository", line 11, in &lt;module&gt;     from softwareproperties.SoftwareProperties import SoftwareProperties, shortcut_handler   File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 27, in &lt;module&gt;     import apt_pkg ModuleNotFoundError: No module named 'apt_pkg' Error in sys.excepthook: Traceback (most recent call last):   File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in apport_excepthook     from apport.fileutils import likely_packaged, get_recent_crashes   File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in &lt;module&gt;     from apport.report import Report   File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in &lt;module&gt;     import apport.fileutils   File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in &lt;module&gt;     from apport.packaging_impl import impl as packaging   File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 23, in &lt;module&gt;     import apt   File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in &lt;module&gt;     import apt_pkg ModuleNotFoundError: No module named 'apt_pkg'  Original exception was: Traceback (most recent call last):   File "/usr/bin/add-apt-repository", line 11, in &lt;module&gt;     from softwareproperties.SoftwareProperties import SoftwareProperties, shortcut_handler   File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 27, in &lt;module&gt;     import apt_pkg ModuleNotFoundError: No module named 'apt_pkg'   Thanks for help Android: How to open a specific folder via Intent and show its content in a file browser? Content replacement from external website How can I prove the inequality $|xy|\leq\frac{1}{2}(x^2+y^2)$  I have tried substitute $x,y$ for numbers, which turns out right, but I don't know how to reason here.  Thanks in advance! Solve a system of equations with Euclid's Algorithm Approximate order statistics for normal random variables Recursive bash script to collect information about each file in a directory structure How do I work recursively through a directory tree and execute a specific command on each file, and output the path, filename, extension, filesize and some other specific text to a single file in bash. Strange artifacts along window borders after waking computer from sleep mode So I took an introductory abstract algebra course a few semesters ago, and we were shown that groups and rings can both be made into products, i.e. if I have some group $G$ (resp. ring $R$) and some indexing set $I$, then I can make a group $G^{I}$ (resp. ring $R^{I}$) with the appropriate cardinality. However, it was also demonstrated that for fields, you cannot keep the multiplicative inverse under a product structure, i.e. if I have fields $F_{1}, F_{2}$, then $F_{1} \times F_{2}$ will still be a ring, but you will not (not just "not in general", but won't) have multiplicative inverses for all non-zero (i.e. not $(0, 0)$) elements, as you could pick $(0, x)$, where $x \neq 0$. According to Wikipedia, an ultraproduct will preserve field structure, but I'm not sure what the cardinality of $\prod_{i \in I} F_{i} / \mathscr{U}$ would be in general.  I saw  that said you could make a field of arbitrarily large cardinality by extending a given field through throwing in a whole bunch of "transcendental" elements. The example given was that if I had $\mathbb{Q}$, I could start by dumping in the complexes, but then I suppose after that I'd just start throwing in dogs and cats or something; I'm really not sure what that responder meant, and ceteris paribus, my dogs tend to stay inside, so I'd rather keep them out of my fields, particularly the large ones the thread was interested in.  Moreover, the thread mentioned earlier seemed more concerned with just making the fields big. My question is a bit more nuanced: Given any cardinality $\kappa &gt; 1$, can I generally construct a field $F$ of a cardinality $\kappa$? Moreover, how vague do I have to be about it (i.e. do I have to use some really choicy methods, or can I make it a bit more straightforward)?  Thanks.  EDIT: Sorry. I am aware that for finite fields, you are limited to powers of primes. I meant for infinite cardinals. Show that the boundary of a set equals the boundary of its complement $\newcommand{\bdy}{\operatorname{bdy}}$  I'm trying to show that $\bdy(A) = \bdy(A^c)$.  I know that $\bdy(A) = \operatorname{closure} A \setminus \operatorname{int}(A) = (\operatorname{int}(A^c))^c \setminus \operatorname{int}(A)$, but I don't know where to go from there.  Any help or hints would be very much appreciated. I am trying to use squared loss to do binary classification on a toy data set. I am using mtcars data set, use mile per gallon and weight to predict transmission type. The plot below shows the two types of transmission type data in different colors, and decision boundary generated by different loss function. The squared loss is $\sum_i (y_i-p_i)^2$ where $y_i$ is the ground truth label (0 or 1) and $p_i$ is the predicted probability $p_i=\text{Logit}^{-1}(\beta^Tx_i)$. In other words, I am replace logistic loss with squared loss in classification setting, other parts are the same. For a toy example with mtcars data, in many cases, I got a model &quot;similar&quot; to logistic regression (see following figure, with random seed 0).  But in somethings (if we do set.seed(1)), squared loss seems not working well.  What is happening here? The optimization does not converge? Logistic loss is easier to optimize comparing to squared loss? Any help would be appreciated.  Code d=mtcars[,c(&quot;am&quot;,&quot;mpg&quot;,&quot;wt&quot;)] plot(d$mpg,d$wt,col=factor(d$am)) lg_fit=glm(am~.,d, family = binomial()) abline(-lg_fit$coefficients[1]/lg_fit$coefficients[3],        -lg_fit$coefficients[2]/lg_fit$coefficients[3]) grid()  # sq loss lossSqOnBinary&lt;-function(x,y,w){   p=plogis(x %*% w)   return(sum((y-p)^2)) }  # this random seed is important for reproducing the problem set.seed(0)  x0=runif(3) x=as.matrix(cbind(1,d[,2:3])) y=d$am opt=optim(x0, lossSqOnBinary, method=&quot;BFGS&quot;, x=x,y=y)  abline(-opt$par[1]/opt$par[3],        -opt$par[2]/opt$par[3], lty=2) legend(25,5,c(&quot;logisitc loss&quot;,&quot;squared loss&quot;), lty=c(1,2)) How is it possible to use the GNU find command to match several file types at a time (one search command)?  The man page says:  -type c     File is of type c:     b      block (buffered) special     c      character (unbuffered) special     d      directory     p      named pipe (FIFO)     f      regular file     l      symbolic link; this is never true if the -L option or the -follow            option  is in  effect,  unless  the  symbolic link is broken.  If            you want to search for symbolic links when -L is in effect, use            -xtype.     s      socket     D      door (Solaris)   and I want to search for files (f) and symbolic links (l) and pipe it to another process. How can I search for both at the same time?  I have tried  find -type fl | … find -type f -type l | … find -xtype f -type l | …   I know a workaround would be to use a subshell  (find -type f; find -type l) | …   but I just want to know if it is possible. A tank of 425 liters capacity has been filled with water through two pipes, the first pipe having been opened 5 hours longer than the second. If the first pipe were open as long as the second pipe, the first pipe deliver half the amount of water delivered by second pipe; if the two pipes were open simultaneously, the tank would be filled up in 17 hours. How long was the second pipe open?    a. 10 b. 12 c. 15 d. 18 I am unable to figure out simple solution to add "Bookman Old Style"  as a main font in my latex document. I have used below line but does not give me required font.  \usepackage{bookman}   Could not find any Simple correct answer for this. Pl. suggest how to do it.  I am using windows, pdflatex.  thank you A closed form for the sum $S = \frac {2}{3+1} + \frac {2^2}{3^2+1} + \cdots + \frac {2^{n+1}}{3^{2^n}+1}$ is ... Is transferring to another university an option for an unhappy PhD student? I've heard of people transferring between graduate schools because of their advisor moving to another school and taking their students with them.   Do students ever transfer for other reasons? If a student isn't happy at the school they choose, could transferring be an option? Presumably they would frame it as something positive such as "turns out I really want to work with Professor X" rather than "I hate my school", but does this ever happen? Is there a certain timeframe in which this is possible? (Assume it's a 5 year PhD program.)  If the answer varies by subject please mention the subject in your answer.  (Context: many friends have told me that if it turns out I'm not happy with my choice, I can always transfer. My impression is that this is actually difficult since many schools don't accept transfer students and in any case not being able to stick with a program looks bad -- but I don't have evidence either way so wanted to ask people who are in academia. Of course the ideal would be to pick a school one is happy with in the first place!) Relevance of cycle detection in Pollard's rho integer factorization algorithm I've recently learned about Pollard's rho factorization algorithm, and the way I understand it, it works by using a pseudorandom sequence of integers $x_{k}$ ranging from $0$ to $n-1$, where $n$ is the number to be factored, to find repetitions in an unknown sequence $y_{k} = x_{k} \bmod p$, where $p$ is an unknown, non-trivial factor of $n$. Such a repetition $y_{i}=y_{j}$ occurs when $x_{i}\equiv x_{j} \bmod p$, which can be detected by checking whether $\gcd(x_{i}-x_{j}, n)\gt 1$.  From what I could find on the Internet, Floyd's cycle detection algorithm or a variant thereof is used to find such repetitions. And the reason for this is what I don't understand.   First, Floyd's algorithm requires that each element in the sequence depends solely on the element before it, which, even if it is the case for $x_{k}$, is not necessarily the case for $y_{k}=x_{k}\bmod p$. For example, assuming we want to factorize $6$, let's take the sequence $5, 3, 2, 4, 1, 0, 5, 3, 2, 4, 1, 0,\ldots$. The cycle period is $5, 3, 2, 4, 1, 0$, where every element is contained only once. However, if we take this sequence $\bmod 2$, we get $1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0,\ldots$. Floyd's algorithm cannot be applied here to find the cycle period $1, 1, 0, 0, 1, 0$. Besides, we are not even interested in a cycle, only in repetitions. Whether we find the congruence $\bmod 2$ between $5$ and $3$, $5$ and $1$, or $4$ and $2$ in the first sequence is irrelevant.   Please correct me if my understanding of Pollard's rho algorithm as described above is wrong. But if it is not, it seems to me that one could just as well try out some random numbers between $2$ and $n-1$ and see if they share a divisor with $n$ other than $1$. So what is the benefit of using a cycle detection method like Floyd's algorithm?  I also found , but it is not answered, and the comment on the question does not really answer the question either. How to get full query text from performance_schema.threads? According to : Access to the threads table does not require a mutex  and has minimal impact on server  performance. The other sources have negative performance consequences because they require a mutex.   So yes, I want to use threads table to examine running queries. The trouble is, the PROCESSLIST_INFO column does not contain the full query. It just contains a truncated version of the query. There is a flag viz performance_schema_max_sql_text_length which controls how many bytes are allocated for the SQL query. But it seems to affect the events_statements_history_long table. There is no change in the thread table output. There is also the events_statement_current table. But it is not clear if accessing that table affects performance or not.