I am running a random forest on a binary classification variable using about 30 explanatory variables. Please have a look at the screenshot below. You see that the out-of-bag errors for class 2 increases as the number of trees increases. This looks weird, as I expect the out of bag error to decrease as more trees are added.  Can somebody explain this or point me in the right direction?
Software implementations of random forest classifiers have a number of parameters to allow users to fine-tune the algorithm's behavior, including the number of trees $T$ in the forest. Is this a parameter that needs to be tuned, in the same way as $m$, the number of features to try at each split (what Leo Breiman calls mtry)?
What is the easiest way to resolve apt-get BADSIG GPG errors? Var[A+B+C] = Var [A] + Var [B] + Var [C] I know that this relationship is correct when A,B and C are pairwise independent. However, I'm finding it difficult to calculate it.  Let's say that: Var [A] = Var [B] = Var [C] = 0.25. How can I prove that Var[A+B+C] = 0.75?  I started to work with the formula: Var[A+B+C] =E[(A+B+C)^2]−(E[A+B+C])^2 but I got stuck.  Thanks! How do I reboot a Ubuntu Server from the command line? sudo reboot now never seems to work for me. Because its a server, I don't have a window manager installed, so I can't do it from a GUI (which always seems to work).    I've had the problem for years on different versions of the operating system. It happens in virtual machines and on real metal. The same problem exists with sudo shutdown now, too.  I've lived with it in the past. The difference now is I don't want to just hit the power button because I might lose data. Adding 3 electron spins I've learned how to add two 1/2-spins, which you can do with C-G-coefficients. There are 4 states (one singlet, three triplet states). States are symmetric or antisymmetric and the quantum numbers needed are total spin and total z-component.  But how do you add three 1/2-spins? It should yield 8 different eigenstates. Which quantum numbers do you need to characterise the 8 states?  It is not as easy as using C-G-coefficients and the usual quantum numbers as for the total momentum the doubly degenerate 1/2 state and quadruple degenerate 3/2 state can describe only 6 or the 8 states. You will need an additional quantum number for the degeneracy.  So how do you get the result?  (I actually tried out myself with a large 8x8 matrix. The total spin 1/2 is each doubly degenerate. For the additional quantum number I chose the cyclic permutation. Spin 1/2 states are neither symmetric nor antisymmetric. But what is the usual way to derive this?)  EDIT: For reference I'm adding my results for up to 4 spins from some time ago:   If you recall the basics of quantum mechanics with matrices it is actually a straightforward matrix diagonalization and requires no specialized knowledge. However, you still need to find an additional operator which breaks degeneracy. I chose the cyclic permutation, which seems to do the job. Please refer to the below answer, since I haven't checked all details. Getting absolute path of a file Can ordered list produce result that looks like 1.1, 1.2, 1.3 (instead of just 1, 2, 3, ...) with css? This is a Q&amp;A so I answer it myself. I searched for an answer to this question for ages and didn't find anything so I'll add this here if anybody else struggles with the same issue.  So, how can I merge two edge loops to one? I do not want to connect them (I have seen many answers that suggest to just bridge the edge loops), nor do I want to merge each vertex by hand. I just want each vertex to be merged with the closest opposing vertex.  Also, I find it highly unpractical and in most situations useless to remove doubles after moving the vertices to overlap each other by scaling and moving the edge loops. This is another common suggested answer. Creating additional Virtual Host Ubuntu Server How to escape a single quote? This works fine:  sed -i 's#    @driver.find_element(:xpath, "//a\[contains(@href,##' temp_spec.rb   against a source of  @driver.find_element(:xpath, "//a[contains(@href,'change_district')]").click   I am just left with:  'change_district')]").click`   but when I try to add a single quote at the end it fails:  sed -i 's#    @driver.find_element(:xpath, "//a\[contains(@href,\'##' temp_spec.rb  syntax error near unexpected token `('   I am using \' to escape the single quote.  Note that I am using a # as a delimiter instead of the normal / delimiter as there are /'s in the text. I'm travelling to country X. I want to install an application which isn't available in my country, but is available in country X; but I prefer to download and install it in advance, while the data connection is still cheap.  Unfortunately, the Play Stores does not allow me to install this app. Is there any way to circumvent this limitation? Why is there a peeking duck in my profile pic? In , you may see something odd: a peeking duck.    I've just recently uploaded this new profile picture of mine. I checked it after the upload and everything's fine. After a few hours, I opened my profile and there it is, the duck has somehow become afraid of the people viewing it.  Is this a bug, a feature, or is it just the duck?  I am about to re-upload my profile pic, but I've decided to drop first this topic to meta.  And if you're curious,  is the original picture.    ADDITIONAL: I've used the non-gravatar way to upload the picture.  ADDITIONAL 2: The problem only shows in the profile view. No problem in chat, less info profile view, and in the questions and answers.  UPDATE: Re-uploaded picture. Status normal (for now, at least). If $\gcd(a,b)=1$, then $\gcd(a+b,a^2 -ab+b^2)=1$ or $3$. Hint:  $a^2 -ab +b^2 = (a+b)^2 -3ab.$  I know we can say that there exists an $x,y$ such that $ax + by = 1$.  So in this case, $(a+b)x + ((a+b)^2 -3ab)y =1.$  I thought setting $x = (a+b)$ and $y = -1$ would help but that gives me $3ab =1.$  Any suggestions? How can I view the time of a text message in iOS 7? In iOS 7, I've noticed that some SMS/MMS messages have a date and time stamp displayed above the message.  Although this is useful, not all text's in the list receive such a date and time stamp.  Is there a way that I can view the date and time for ever text message? Question about Subrings and integraly closed Suppose that $A, B, C$, and $D$ are sets with the cardinalities related as  $|A|=|C|$ and $|B|=|D|$. Prove that the cardinality of $A\times B$ is equal to the cardinality of $D\times C$.  I know that I must prove the bijection of the function $f: A \times B \to C \times D$, but I am not sure how to say this? Can anyone help me? MacBook Pro Trackpad Suddenly Stopped Working Completely The trackpad on my Macbook Pro of 2 years has suddenly stopped working out of blue.  The trackpad doesn't move, respond to any gestures nor do any clicks work. This is really frustrating as I used gestures a lot to navigate around my laptop, and even though I use a bluetooth mouse it makes using my laptop unnecessarily laborious.  Does anyone know what may be causing the problem, and any solutions? I bought a Minecraft account for my little brother for Christmas, and I'd like to play with him on my server every now and then. If I log in while he's on, however, it kicks him off since we have the same username. Is there any way to change my username so that I can play with him, or anything I can do so that we can both play together using this account on my server?  I'm open to anything that could let us play, whether it be username changes, server property changes, etc. I am trying to balance underbraces in the equation below, how can I ensure that both underbraces at the same depth?  \begin{equation} y = \underbrace{ \left [ x^2 + r^2 (a^2+\frac{a^{0.3}}{b}) \right]}_\text{growth rate} \times  \underbrace{ C_0}_\text{initial} \end{equation} Install GNOME Shell extensions from terminal Is there a way to install GNOME extensions from terminal, for example dash to dock? The way I do it now is to go into Ubuntu Software app store and install it. Why Normality assumption in linear regression