Sometimes I encode categorical features as binary values - one feature per possible category value indicating whether that feature name matches the original category value (i.e. one-of-K scheme).  Now these values are linearly dependent, since obviously their total sum is 1.  Does this linear dependence matter for linear SVM, kernel SVM, logistic regression, etc.? Where does it matter so that I need to remove one of the features? Does it cause problems for normal linear regression? For which methods does it not make a difference?
My understanding is that in machine learning it can be a problem if your dataset has highly correlated features, as they effectively encode the same information.  Recently someone pointed out that when you do one-hot encoding on a categorical variable you end up with correlated features, so you should drop one of them as a "reference".  For example, encoding gender as two variables, is_male and is_female, produces two features which are perfectly negatively correlated, so they suggested just using one of them, effectively setting the baseline to say male, and then seeing if the is_female column is important in the predictive algorithm.  That made sense to me but I haven't found anything online to suggest this may be the case, so is this wrong or am I missing something?  Possible (unanswered) duplicate:
I have recently installed ubuntu 11.10. But when i try to install a software it tries to 'updating cache' but after a while, it stops, showing:                            Failed to download repository information                           Check your internet connection   so, now i am totally unable to install any software in my ubuntu.  Please,let me know how to solve the problem. Adjectives or compound noun? Look and you shall find (a correlation) Proving that $m+n\sqrt{2}$ is dense in $\mathbb R$ I am having trouble proving the statement:     Let $$S = \{m + n\sqrt 2 : m, n \in\mathbb Z\}$$ Prove that for every $\epsilon &gt; 0$, the intersection of $S$ and $(0, \epsilon)$ is nonempty. adding a point in a manipulate command To find:  $$\int \sqrt{1+\sin(x)} dx$$  What I  tried:  I put $\tan(\frac{x}{2}) = t$, using which I got it to:  $$I = 2\int \dfrac{1+t}{(1+t^2)^{\frac{3}{2}}}dt$$  Now I am badly stuck. There seems no way to approach this one. Please give a hint. Also, can we initially to some manipulations on the original integral to make it easy? Thank you. When should N-Gons be used, and when shouldn't they? Can a US citizen leave and enter the US using a foreign passport? I am a dual citizen. I have both a US passport and a non-US passport. I live in the US. My US passport is currently being processed for renewal. I am unsure whether I will receive my passport in time for a trip that I have scheduled. Could I use my non-US passport to leave the US and return? I have never entered the US with my non-US passport. There is no immigration leaving the US but I still need to scan my passport for ticketing. Will the airline refuse me a ticket? I know that in this situation returning with a non-US passport can be problematic as well, but will I be able to leave at all? Note that I am traveling to a country which neither of my passports are from. I was looking for proofs using Calculus for the area of a circle and come across this one $$\int 2 \pi r \, dr = 2\pi \frac {r^2}{2} = \pi r^2$$  and it struck me as being particularly easy. The only other proof I've seen was by a teacher and it involved integrating $x = \sqrt{r^2 - y^2}$ from $-1$ to $1$, using trig substitutions and then doubling the area to get $\pi r^2$ but the above proof seemed much more straight forward.  Is it a valid proof, or is it based on circular logic or some other kind of fallacy? 13.04 - more than four workspace shortcuts in GNOME Flashback (No effects) I'm using GNOME Flashback (No effects) on Ubuntu 13.04 and I've got six workspaces however when entering System Settings -> Keyboard -> Shortcuts -> Navigation I only see options to address the initial four.  It used to be options up to 12 workspaces there and as I certainly don't need that much, I want to have at least enough for the amount currently active.  How can I restore or add more shotcuts specifically to navigate and move windows to workspace 5 and 6? How to change the title of ToC? I need to change default title of ToC. Is it possible with titlesec package? Here is my MWE:  \documentclass{book}  \usepackage{titlesec} \titleformat{\chapter}{\normalfont\Large\scshape}{\thechapter}{1em}{} \vspace{6pt}]  \usepackage{lipsum}   %-------------------------------------------------------------------------  \begin{document}   \newpage \thispagestyle{empty} \tableofcontents \thispagestyle{empty} \newpage \thispagestyle{empty}  \setcounter{footnote} {0}\chapter*{{\fontsize{11}{14}\selectfont\normalfont{Author1} \\ {\scshape\Large Title}}} \addcontentsline{toc}{chapter}{\normalsize\normalfont{Author1} \\ \normalfont\scshape{Title}} \thispagestyle{empty} \Author{Author1} \Title{Title} \lipsum \newpage \thispagestyle{empty}    \end{document} Why does ltablex skip a number in captions? The below example presents two tables with an tabularx environment (taken from package ltablex) and a caption. After each tabularx-table, the table counter skips one, as if both the caption and the tabularx environment increase it, while the latter shouldn't.  \documentclass{report} \usepackage{ltablex} \begin{document}  \begin{table} \caption{Caption 1.} % "Table 1" \begin{tabularx}{\linewidth}{|c|} empty table \end{tabularx} \end{table}  \begin{table} \caption{Caption 2.} % "Table 3" \begin{tabularx}{\linewidth}{|c|} empty table \end{tabularx} \end{table}  \end{document}   My reputation doesn't allow me to upload a picture, but the captions are Table 1 and Table 3 respectively. I installed Ubuntu 12.10 and entered a password in SeaHorse. I would like to remove the password of "Default" but I get this error :  GDBus.Error:org.freedesktop.Secret.Error.NoSuchObject: The collection does not exist   Is there a fix or a way to bypass modify the password ? How to text-to-speech output using command-line? How to get speech output from entered text by using command-line?  Also facility to change speech rate, pitch, volume etc using simple command. How to automatically create large number of columns in Excel 2013 I would like to start a new excel spreadsheet, create a column named Column1, and quickly fill in increments, (Column2, Column3 etc) up to Column500. Is there an easy way to do this?   Also is there an easy way to afterwards select all 500 columns and add 10 rows of data to all of them? Can I permanently block an update (non-driver) that will not install on my machine on Win10 pro? I have an update to Visual Studio 2010 that will NOT update and has failed hundreds of times. Manually installing it also fails, and no source has been found for manually getting this very old patch to install on Windows 10. I believe the problem is that Microsoft simply hasn't re-tested KB2890573 at all and it doesn't install on Win10 ver 1511 at all, anymore.  I do not want to use the MS utility that will postpone this update for a while. I want to permanently block it so it does not appear in the windows update list ever again. Can't read filenames in save dialog box. Names are too faint I want to click on file to inherit the name for the file being saved. I can't read file names in the dialog box because the color is too faint. This is the same question as   That question does not have an answer but I don't have enough points to interact there so I have to post a new question.    Edited to add screen shots I tried to calibrate the monitor which no effect and did not change the readability of "unavailable" file names. I have added screenshots of previous operating systems to compare: Please tell me how Mojave is not to blame here: The Problem For a small mass a distance $R_i$ away from the center of the Earth, how long would it take for the object to fall to the surface of the Earth, assuming that the only force acting upon the object is the Earth's gravitational force?  Relevant Information The following discussion seems to have solved exactly the same problem:   However, upon working out the mathematics, I'm not exactly sure how to evaluate the constant of integration.   A Partial Solution $$ F=\frac {-GMm}{s^2} $$ $$ a=\frac {-GM}{s^2} $$ $$ \frac {dv}{dt} = \frac {-GM}{s^2} $$ Multiplying by $v$ and then integrating by $dt$ on both sides, we have $$\frac {1}{2} v^2=\frac {GM}{s} +c_1$$ where $c_1$ is a constant of integration. Substituting initial conditions of $v=0, s=R$, we have $$\frac {1}{2} v^2=GM(\frac {1}{s}-\frac{1}{R})$$  At this point of time, when I use Wolfram Alpha, I get  $$c_2+\sqrt{\frac{2}{R}}t=\frac{\sqrt{s}(s-R)+R\sqrt{R-s}\times{\tan^{-1}(\sqrt{\frac{s}{R-s}})}}{\sqrt{GM(R-s)}}$$  where $c_2$ is a constant of integration. Substituting initial conditions of s=R, t=0, we find that the term $$\tan^{-1}(\sqrt{\frac{s}{R-s}})$$ is undefined. At this point, I'm stuck. Any ideas on where I've made the mistake here?  (For those interested, this question was inspired by the Greek myth which states that a bronze hammer dropped from heaven would take 9 days to hit the Earth and would reach on the tenth). Why does kworker cpu usage get so high? I recently installed Ubuntu 12.04 on my Samsung laptop alongside Windows 7. Whenever I use Ubuntu (even when its idle) kworker uses almost 90% of one of 8-cores. Even though it doesn't really affect my usage, it bugs me and I am afraid of that it might harm my processor. I even tried installing another Linux distro (Linux Mint), and kworker caused the same problem. So I don't know what to do. I would really appreciate your  help. How can I show that "A center of a free group that is non-cyclic is trivial" ?