When I use this command :  &gt; chm &lt;- grid_canopy(gro, 1, pitfree(c(0,2,5,10,15), c(0,1), subcircle = 0.2)) Processing [-------------------------------------------]   0% (1/341) eta:  8mError: filename exists; use overwrite=TRUE   I have an error because the file exist. How can i add the overwrite argument to grid_canopy because when i use this command :  chm &lt;- grid_canopy(gro, 1, pitfree(c(0,2,5,10,15), c(0,1), subcircle = 0.2, overwrite = TRUE)   I receive this error :  Error in grid_canopy(gro, 1, pitfree(c(0, 2, 5, 10, 15), c(0, 1), subcircle = 0.2),  :  unused argument (overwrite = TRUE)
I have a small issue with configuring the lidR  for parametrizing the extracted raster files with grid_metrics() function.  My question is how to set in the catalog options that:   be able to overwrite the results with a second run if I want to run my script several times and I do not want to name each output differently. instead of .tif I would like to get .grd files as output.   My current code (which is working) is the following:  normalizedctg = catalog(workingdirectory) opt_output_files(normalizedctg) &lt;- paste(workingdirectory,"/clipped/normalized/{XLEFT}_{YBOTTOM}_height",sep="") height = grid_metrics(normalizedctg, max(Z),res = resolution)   But with a second run on the same code I get the following error:  Error in .getGDALtransient(x, filename = filename, options = options,  :    filename exists; use overwrite=TRUE
Why do we use this definition of "algebraic integer"? A number is an &quot;algebraic integer&quot; if it is the root to a monic polynomial with integer coefficients. Artin says (Algebra, p. 411):  The concept of algebraic integer was one of the most important discoveries of number theory. It is not easy to explain quickly why it is the right definition to use, but roughly speaking, we can think of the leading coefficient of the primitive irreducible polynomials $f(x)$ as a &quot;denominator.&quot; If $\alpha$ is the root of an integer polynomial $f(x)=dx^n+a_{n-1}x^{n-1}...$ then $d\alpha$ is an algebraic integer, because it is a root of the monic integer polynomial $x^n + a_{n-1}x^{n-1} + ... + d^{n-1}a_0$. Thus we can &quot;clear the denominator&quot; in any algebraic number by multiplying it with a suitable integer to get an algebraic integer.  When I first learned of algebraic integers, I looked online and saw some hints that maybe they were used to prove the Abel-Ruffini theorem. So I put off questioning their usage for a while; I now think I understand one proof of this theorem (the one at the end of Artin's Algebra) and it has nothing to do with algebraic integers (that I can tell). So basically: why is it important if a number is an algebraic integer? I think I understand what he's saying about the relationship between roots of integer polynomials and algebraic integers, but I fail to see why this is &quot;one of the most important discoveries of number theory.&quot; Find the functions $f:\Bbb R_*^+ \to \Bbb R_*^+$ such that:  $$f(x)f \left(\frac{1}{x}\right)=1$$ Are there any coding style guidelines for LaTeX? If I have bought 3 tickets for the same flight, can I bring three times the cabin allowance allowed per ticket?  The way I see it I am doing the airline a favor  Related: jQuery scrolltop firefox not working How can I have a pointer to the next struct in the definition of this struct:  typedef struct A {   int a;   int b;   A*  next; } A;   this is how I first wrote it but it does not work. I am trying to get an intuitive idea of how the  affects Quantum computation. My understanding is that given a qubit $Q$ in superposition $Q_0 \left| 0 \right&gt; + Q_1 \left| 1 \right&gt;$, NCT states another Qubit $S$ cannot be designed such that $S$ is equivalent to the state of $Q$.   Now the catch is, what does Equivalent mean? It could mean either that:   $S = S_0 \left| 0 \right&gt; + S_1 \left| 1 \right&gt;$ such that $S_0 = Q_0, S_1 = Q_1$. Or it could mean that $S = Q$, meaning that if $S$ is observed to be some value ( for example 0) then $Q$ MUST be that same value, and vice versa.    So it seems that point 2, occurs anyways in entangled systems (particularly cat-states), so I can eliminate that option and conclude that that No Cloning states, given a qubit $Q$, it's impossible to make another qubit $S$ such that:  $S = S_0 \left| 0 \right&gt; + S_1 \left| 1 \right&gt;$ such that $S_0 = Q_0, S_1 = Q_1$.  Is this correct? Hyperlinks to web sites using anchors sometimes don't work I am a Indian citizen in the United States on a F-1 visa.  For the summer break, I am traveling (round-trip) from Chicago to New Delhi via Dusseldorf-Frankfurt by Lufthansa airlines. My onward Journey would be on July - 8 and return Journey on Aug - 11.  My layover will be of 1 hour 10 mins in Frankfurt and 3 hours in Dusseldorf.  I would like to know if I require Category A or Category B Visa. If not, what type of visa do I require for the Schengen visa for my transit. How I can apply for the same?  I tried to find slots in German consulate but all slots are full before my departure date. If I don't get the Schengen visa, I cannot travel and will loose all the fare (since my ticket is a non-refundable ticket). Is there any other way I can tackle this situation. Why are .goutputstream-xxxxx files created in home folder? I find a lot of files with names of the like  .goutputstream-xxxxx   where xxxxx are some alphanumeric characters.  Here is a screenshot of the home folder    Any idea why I should keep these or can I remove and also stop further creation? How to enable bullet points when using the presento beamer theme? I have the problem that when I use an itemize list and the , there are no bullet points.  Here is a minimal working example (requires the  not available on CTAN to be downloaded first):  \documentclass{beamer} \usepackage{config/presento} \begin{document} \begin{frame} \begin{itemize} \item ... \item ... \item ... \end{itemize} \end{frame} \end{document}     How to fix this problem? Javascript infamous Loop issue? If you shine a light away from the center of a Schwarzchild black hole, will it stay still? $$ A $$  Light is travelling away from the absolute center of the Schwarzchild black hole (i.e. none of that spinning/stretching field) at $\ C $, and so shouldn't $\ \Delta C$ need to be greater than $\ C $ in order for the light to collapse into the black hole, therefore violating the relativistic limit of $\ C $?    It seems like light would just 'hover' right in the center of a black hole then. Because if it goes away from it, the event horizon pulls it back, and if it goes into it, the velocity change must be greater than $\ C $ which violates general relativity; so technically there's no way for the light to move away, and so it would just be still.  The thing is that the light must move at the speed of light or general relativity doesn't work. It's massless... But in the center of a black hole, if the above is true (it can't move or escape), then it is not travelling at the speed of light. So it cannot be still.  It cannot be spinning in a constant orbit either, because that would require velocity in an outward angle. And it cannot move in an outwardly fashion, only in an inwardly one.  Is it spinning in an infinitely decaying spiral towards the center?  If so what happens to it if and when it reaches the direct and complete center, i.e. The case of it being 'shot' from the center.    $$ B $$  If you shot light at an angle towards a black hole, but not directly to the center of it  then that light from the outside will eventually become the same as the light that I said was shot from the center to the outside; because in both cases, they end up in an infinitely decaying spiral.    If so it would end up exactly like the light in the above paragraph, so then we need to figure out what happens to that light to figure this one out, or vice versa.    $$ C $$  If you shot light directly towards the center of a black hole it would have no spiral to decay into, so therefore it must stop at some point in the center of a black hole. If it stops though, it loses it's momentum and violates general relativity again because it's energy "disappears".    If so then it violates conservation laws. So I'm assuming this simply is not true.    Is the light travelling into a black hole somehow still travelling at the speed of light, in every direction possible where that direction keeps it facing towards the center?  If so, why is there not a point at which the only thing left for the light to do is stay still, since all other paths would increase the distance between it and the black hole's center, and therefore become Case A. And if there isn't, what would happen if there was?  Also, if it's a time and observation answer where it supposedly takes and infinite amount of time for C to hit the center, wouldn't it be the case that the black hole is 'eating' all of the available light in the universe and keeping it in stasis?  Also, what happens in a Kerr black hole then? Does it just rip the field of time/gravity at an angle such that the light would never get closer than the center? Is there to make the login screen appear on the external display in 18.04? If $A$ and $B$ are positive definite, then is $B^{-1} - A^{-1}$ positive semidefinite? I've been modeling a hermit crab and I don't know why but some areas of the mesh are really dark on some spots, like the legs and the claws.   I hope you can help me fix it. Tools to get a pictorial function call graph of code What makes a photo a good photo? I don't know if this is a stupid question, this just came across my mind.  Imagine a photo of a dog yawning.  Someone could say that is a very good photo as it is taken just at the right moment, from a perfect angle (eg. level with the dog) and it has a shallow depth of field focusing on its face.  Someone else might dislike it because unfortunately the dog is ugly.  So from that example I could say people look at the following elements when judging a photo (but I could be wrong):   The timing (if it's taken at the right moment) The angle it's taken from (composition?) DOF (composition?) The subject (eg. whether the dog is pretty)   I am interested to know what experts think the elements you look at when judging whether a photo is a good photo.  Thanks in advance for your comments. Characterization convex function. php function for collating external variables into a single object regardless of GET or POST I recall reviewing someone else's PHP code once and he had a function or class method that rolled all GET and POST variables into a single plain old object that could then be passed around. If the same name-value pair appeared in both GET and POST, POST would win.  Is there a well-coded PHP add-on out there of any sort that does exactly this?