Why online brokerages sometimes allow free ETF buying ETFs trade just like stocks, so I wonder how come questrade lets customers trade ETFs for free whereas they charge commission on stock trading? Any guesses? Furthermore, only buying is free but selling is not, which is all the more confusing.  Do they mark up the spread? Or are ETFs so liquid that the broker can afford not to charge a fee. I can ask the broker of course, but usually they say 'customer loyalty, customer appreciation etc.' and things like that.
No transaction fee ETF trades - what's the catch? I just noticed TD Ameritrade has program where you can trade from a list of ETFs with zero fees.  Sounds like it could save me a bit of money, but my cynical side wonders how they make money off such a program...  Is it a loss leader? (They entice me to have an account there, and then make money off the other trades I make?)  Or do they simply want to grow the size of their asset base -- what is the mechanism by which they make money on the funds that I have in my account?  Edit: in case it wasn't clear in the original question above, this is an ongoing program for free ETF transactions -- not a one-time deal for some number of free trades when you open an account. I have had an account there for years and I'm eligible to participate -- it's not a program explicitly designed just to gain new accounts.
How to switch window controls to the left (Gnome Shell)? Is there a way to the switch gnome-shell window buttons to the left? I've gotten so used to them being on the left that them being on the right has thrown me way off.  (gnome shell has them defaulted to the right corner) How to hide "internal" polygon boundaries? Fan is always on, CPU usage is rather low and can't find the fan or thermal_zone proc files I have an Asus N76VB notebook with Ubuntu 14.04 and TLP for power managment. However, the fan is always on. It's not really loud, but it's annoying. My CPU usage is around 1-2%. It's clocked at 1.20 GHz.  I've added acpi=force to my boot parameters but it doesn't change anything.  /proc/acpi/fan: No such file or directory /proc/acpi/thermal_zone: No such file or directory   I've loaded all Asus ACPI modules.  lsmod | grep asus:  asus_nb_wmi            16990  0  asus_wmi               24191  1 asus_nb_wmi sparse_keymap          13948  1 asus_wmi video                  19476  2 i915,asus_wmi wmi                    19177  2 mxm_wmi,asus_wmi   Somehow, it can read the temperatures.  sensors:  acpitz-virtual-0 Adapter: Virtual device temp1:        +43.0°C  (crit = +108.0°C)  coretemp-isa-0000 Adapter: ISA adapter Physical id 0:  +44.0°C  (high = +87.0°C, crit = +105.0°C) Core 0:         +44.0°C  (high = +87.0°C, crit = +105.0°C) Core 1:         +42.0°C  (high = +87.0°C, crit = +105.0°C) Core 2:         +39.0°C  (high = +87.0°C, crit = +105.0°C) Core 3:         +39.0°C  (high = +87.0°C, crit = +105.0°C)  asus-isa-0000 Adapter: ISA adapter temp1:        +43.0°C     I really hope someone knows how to solve this. Almost all information I could find was about saving power to create less heat.    I got Intel and NVIDIA (GeForce 740M) graphics but I'm almost anytime on Intel.  $ sudo lshw -c display   *-display                       description: VGA compatible controller        product: 3rd Gen Core processor Graphics Controller        vendor: Intel Corporation        physical id: 2        bus info: pci@0000:00:02.0        version: 09        width: 64 bits        clock: 33MHz        capabilities: msi pm vga_controller bus_master cap_list rom        configuration: driver=i915 latency=0        resources: irq:43 memory:f7400000-f77fffff memory:d0000000-dfffffff ioport:f000(size=64)     fwts fan: bash variables in for loop range I want to print list of numbers from 1 to 100 and I use a for loop like the following:  number=100 for num in {1..$number} do   echo $num done   When I execute the command it only prints {1..100} and not the list of number from 1 to 100. Evaluating a PDF to find an unkown constant Evaluate the PDF to find K  $1 = \int_0^{\infty} \frac{k}{(1+x)^4}$  using u substitution I got:  $u=1+x$ and $du= dx$  $\int_0^{\infty} \frac{k}{u^4} \to \frac{k}{\frac{-1}{3} u^3}$   Since $u^4 du = \frac{u^{-4+1}}{-4+1}=$ $\frac{u^{-3}}{-3}$  which evaluating gives:  $1=\frac{k}{\frac{-1}{3(1+x)^3}} \vert_0^{\infty} \to \frac{-3k}{(1+x)^3} \vert_0^{\infty} = 0 -3k$   and $k= \frac{-1}{3}$  somehow though they came up with $\frac{-k}{3} \frac{1}{(1+x)^3}$ after integrating $\int_0^{\infty} \frac{k}{(1+x)^3}$   Was my approach correct to use substitution? Where does my work go wrong? When is using the past perfect tense not necessary? Determine whether or not a point lies within a rotated rectangle Let $f$ be a real valued, continuous and differentiable function on the real numbers with $f'$ uniformly continuous. Show that $g_n(x)$ with $$g_n(x)=nf(x+1/n)-nf(x)$$ is uniformly convergent to the derivative of $f$.   I cannot figure out how to solve this problem. If anyone could help me for this problem I would be very grateful. My OpenID provider is shutting down; how do I change my Stack Exchange login? Showing diffeomorphism between $S^1 \subset \mathbb{R}^2$ and $\mathbb{RP}^1$ I am trying to construct a diffeomorphism between $S^1 = \{x^2 + y^2 = 1; x,y \in \mathbb{R}\}$ with subspace topology and $\mathbb{R P}^1 = \{[x,y]: x,y \in \mathbb{R}; x \vee y \not = 0  \}$ with quotient topology and I am a little stuck.  I have shown that both are smooth manifolds, and I used stereographic projection for $S^1$, but now I am runing into trouble when I give the homeomorphism between $S^1$ and $\mathbb{RP}^1$ as the map that takes a line in $\mathbb{RP}^1$ to the point in $S^1$ that you get when letting the parallel line go through the respective pole used in the stereographic projection.   If I use the south and north poles I get a potential homeomorphism, but I cannot capture the horizontal line in my image, but when I pick say north and east then my map is not well defined as I get different lines for the same point in $S^1$. Can somebody give me a hint how to make this construction work, or is it better to move to a different representation of $S^1$ ? In a complete metric space with no isolated points, any countable intersection of open dense sets is uncountable? What is the max variance distribution with fixed mean and support Is there a upper bound on the variance for a distribution that is confined say, in $[0,1]$, and has fixed mean $\mu \in [0, 1]$ This has been nagging me for a while and then I saw  asking what the difference is between variables and parameters. In the context of mathematics, what is the difference between  variables constants parameters arguments  I get 1. and 2. confused because, for example the general form of the quadratic function is often expressed $f(x)=ax^2+bx+c, a \neq 0$ and $x$ is the variable so what does that make a,b and c? I assume since math is so rigorous with precise definitions, these have one, but it is also a valid answer that as words they do not have a single precise definition. Modifying Score text in Locate Widget of Flexviewer 2.4? I want to add text where it says "score" to make it more clear that this is an address matching score.    I am using the LocateWidget_US.xml and do not think I can do it here.  I think the place to do it may be in the LocateWidget.mxml in this line????   locateResult.content = getDefaultString("resultScoreText") + " " +   (addrCandidate.score % 1 == 0 ? addrCandidate.score : addrCandidate.score.toFixed(1)); Overfitting a logistic regression model How to split a file according to a column (including header) and rename the generated files? I have a .txt that can be exemplified like this:  NAME | CODE name1 | 001 name2 | 001 name3 | 002 name4 | 003 name5 | 003 name6 | 003   I need to write a script to split this file according to the CODE column, so in this case I'd get this:  file 1: NAME | CODE name1 | 001 name2 | 001  file 2: NAME | CODE name3 | 002  file 3: NAME | CODE name4 | 003 name5 | 003 name6 | 003   According to some research, using awk would work:  $ awk -F, '{print &gt; $2".txt"}' inputfile   The thing is, I also need to include the header to the first line and I need the file names to be different. Instead of 001.txt, for example, I need the file name to be something like FILE_$FILENAME_IDK.txt. Can awakened mind be used with suggestion? Can the warlock class feature "awakened mind" be used in conjunction with the suggestion spell, allowing the warlock to make the suggestion telepathically?  Awakened Mind, Player's Handbook p. 110:     You can telepathically speak to any creature you can see within 30 feet of you. You don't need to share a language with the creature for it to understand your telepathic utterances.   Suggestion, Player's Handbook p. 279:     You suggest a course of activity (limited to a sentence or two) and magically influence a creature you can see within range that can hear and understand you.   If it works with suggestion, would it also work with mass suggestion?  To be clear, I am not asking about the verbal component of the spell, only the method the caster "suggests a course of activity". Matrices that can only be permutation matrices How to prove that if $A$ and $B$ are two $n×n$ matrices with non negative integer entries such that $AB=I$ then $A$ and $B$ are permutation matrices?  Permutation matrices are matrices with the columns just a permutation of the identity matrix. How do I proceed. Can somebody give hint? Is a set without limit points necessarily closed? According to the definition on Rudin' Principles of Mathematicial Analysis, closed set is defined as:      $E$ is closed if every limit point of $E$ is a point of $E$.   Then I have a question: if a set has no limit point, is it necessarily closed? I think this idea doesn't contradict the definition of closed sets. Am I right?  And another question is #10 in Chap.2 of Rudin's:      Let $X$ be an infinite set. For $p\in X$ and $q\in X$, define    $d(p,q)=0$ when $p=q$. Otherwises,$d(p,q)=1$.    I have known that every set in the metric space is closed. To prove it, we can show that the complement of any set is open, which is quite trivial. My question is: how can we prove that every set is closed just by checking according to the definition of closed set, i.e. how can we show that every limit point of any arbitrary set $E$ in the metric space is a point of $E$?   Thanks in advanced! There are no book recommendations for Astrophysics here. I will write my own answer, but I am also interested in what are others' views on the question (I will NOT mark my own answer as the best one).