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• getSymbols and using lapply, Cl, and merge to extract close prices

  - by algotr8der

  I've been messing around with this for some time. I recently started using the quantmod package to perform analytics on stock prices. I have a ticker vector that looks like the following: > tickers [1] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" "XLI" "XLB" "XLK" "XLU" "XLV" [14] "QQQ" > str(tickers) chr [1:14] "SPY" "DIA" "IWM" "SMH" "OIH" "XLY" "XLP" "XLE" ... I wrote a function called myX to use in a lapply call to save prices for every stock in the vector tickers. It has the following code: myX <- function(tickers, start, end) { require(quantmod) getSymbols(tickers, from=start, to=end) } I call lapply by itself library(quantmod) lapply(tickers,myX,start="2001-03-01", end="2011-03-11") > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") [[1]] [1] "SPY" [[2]] [1] "DIA" [[3]] [1] "IWM" [[4]] [1] "SMH" [[5]] [1] "OIH" [[6]] [1] "XLY" [[7]] [1] "XLP" [[8]] [1] "XLE" [[9]] [1] "XLI" [[10]] [1] "XLB" [[11]] [1] "XLK" [[12]] [1] "XLU" [[13]] [1] "XLV" [[14]] [1] "QQQ" That works fine. Now I want to merge the Close prices for every stock into an object that looks like # BCSI.Close WBSN.Close NTAP.Close FFIV.Close SU.Close # 2011-01-03 30.50 20.36 57.41 134.33 38.82 # 2011-01-04 30.24 19.82 57.38 132.07 38.03 # 2011-01-05 31.36 19.90 57.87 137.29 38.40 # 2011-01-06 32.04 19.79 57.49 138.07 37.23 # 2011-01-07 31.95 19.77 57.20 138.35 37.30 # 2011-01-10 31.55 19.76 58.22 142.69 37.04 Someone recommended I try something like the following: ClosePrices <- do.call(merge, lapply(tickers, function(x) Cl(get(x)))) However I tried various combinations of this without any success. First I tried just calling lapply with Cl(x) >lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(myX))) > lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX,start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl(x))) Error: unexpected symbol in "lapply(tickers,myX(x),start="2001-03-01", end="2011-03-11") Cl" > > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl(x)) Error: unexpected symbol in "lapply(tickers,myX(start="2001-03-01", end="2011-03-11") Cl" > Any guidance would be kindly appreciated.

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• Modifying reference member from const member function in C++

  - by Philipp

  I am working on const-correctness of my code and just wondered why this code compiles: class X { int x; int& y; public: X(int& _y):y(_y) { } void f(int& newY) const { //x = 3; would not work, that's fine y = newY; //does compile. Why? } }; int main(int argc, char **argv) { int i1=0, i2=0; X myX(i1); myX.f(i2); ... } As far as I understand, f() is changing the object myX, although it says to be const. How can I ensure my compiler complains when I do assign to y? (Visual C++ 2008) Thank a lot!

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• Scheme Formatting Help

  - by Logan

  I've been working on a project for school that takes functions from a class file and turns them into object/classes. The assignment is all about object oriented programming in scheme. My problem however is that my code doesn't format right. The output it gives me whenever I give it a file to pass in wraps the methods of the class in a list, making it so that the class never really gets declared. I can't for the life of me figure out how to get the parenthesis wrapping the method list to remove. I would really appreciate any help. Below is the code and the class file. ;;;; PART1 --- A super-easy set of classes. Just models points and lines. Tests all of the ;; basics of class behavior without touching on anything particularly complex. (class pointInstance (parent:) (constructor_args:) (ivars: (myx 1) (myy 2)) (methods: (getx () myx) (gety () myy) (setx (x) (set! myx x)) (show () (begin (display "[") (display myx) (display ",") (display myy) (display "]"))) )) (require (lib "trace.ss")) ;; Continue reading until you hit the end of the file, all the while ;; building a list with the contents (define load-file (lambda (port) (let ((rec (read port))) (if (eof-object? rec) '() (cons rec (load-file port)))))) ;; Open a port based on a file name using open-input-file (define (load fname) (let ((fport (open-input-file fname))) (load-file fport))) ;(define lis (load "C:\\Users\\Logan\\Desktop\\simpletest.txt")) ;(define lis (load "C:\\Users\\Logan\\Desktop\\complextest.txt")) (define lis (load "C:\\Users\\Logan\\Desktop\\pointinstance.txt")) ;(display (cdaddr (cdddar lis))) (define makeMethodList (lambda (listToMake retList) ;(display listToMake) (cond [(null? listToMake) retList ;(display "The list passed in to parse was null") ] [else (makeMethodList (cdr listToMake) (append retList (list (getMethodLine listToMake)))) ] ) )) ;(trace makeMethodList) ;this works provided you just pass in the function line (define getMethodLine (lambda (functionList) `((eq? (car msg) ,(caar functionList)) ,(caddar functionList)))) (define load-classes (lambda paramList (cond [(null? paramList) (display "Your parameters are null, man.")] [(null? (car paramList))(display "Done creating class definitions.")] [(not (null? (car paramList))) (begin (let* ((className (cadaar paramList)) (classInstanceVars (cdaddr (cddaar paramList))) (classMethodList (cdr (cadddr (cddaar paramList)))) (desiredMethodList (makeMethodList classMethodList '())) ) ;(display "Classname: ") ;(display className) ;(newline)(newline) ;(display "Class Instance Vars: ") ;(display classInstanceVars) ;(newline)(newline) ;(display "Class Method List: ") ;(display classMethodList) ;(newline) ;(display "Desired Method List: ") ;(display desiredMethodList)) ;(newline)(newline) ;---------------------------------------------------- ;do not delete the below code!` `(define ,className (let ,classInstanceVars (lambda msg ;return the function list here (cond ,(makeMethodList classMethodList '()))) )) ;--------------------------------------------------- ))] ) )) (load-classes lis) ;(load-classes lis) ;(load-classes-helper lis) ;(load-classes "simpletest.txt") ;(load-classes "complextest.txt") ;method list ;(display (cdr (cadddr (cddaar <class>))))

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• Using same onmouseover function for multiple objects

  - by phpscriptcoder

  I'm creating a building game in JavaScript and PHP that involves a grid. Each square in the grid is a div, with an own onmouseover and onmousedown function: for(x=0; x < width; x++) { for(y=0; y < height; y++) { var div = document.createElement("div"); //... div.onmouseclick = function() {blockClick(x, y)} div.onmouseover = function() {blockMouseover(x, y)} game.appendChild(div); } } But, all of the squares seem to have the x and y of the last square that was added. I can sort of see why this is happening - it is making a pointer to x and y instead of cloning the variables - but how could I fix it? I even tried for(x=0; x < width; x++) { for(y=0; y < height; y++) { var div = document.createElement("div"); var myX = x; var myY = y; div.onmouseclick = function() {blockClick(myX, myY)} div.onmouseover = function() {blockMouseover(myX, myY)} game.appendChild(div); } } with the same result. I was using div.setAttribute("onmouseover", ...) which worked in Firefox, but not IE. Thanks!

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• geom_tile heatmap with different high fill colours based on factor

  - by Michael

  I'm interested in building a heatmap with geom_tile in ggplot2 that uses a different gradient high color based on a factor. The plot below creates the plot where the individual tiles are colored blue or red based on the xy_type, but there is no gradient. ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=factor(xy_type))) + scale_fill_manual(values=c("blue", "red")) The plot below does not use the xy_type factor to choose the color, but I get a single group gradient based on the xy_avg_value. ggplot() + geom_tile(data=mydata, aes(x=factor(myx), y=myy, fill=xy_avg_value)) Is there a technique to blend these two plots? I can use a facet_grid(xy_type ~ .) to create separate plots of this data, with the gradient. As this is ultimately going to be a map (x~y coordinates), I'd like to find a way to display the different gradient together in a single geom_tile map.

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• UNIX Shell-scripting: UDV

  - by Myx

  I am writing a simple unix shell script: #!/bin/bash # abort the script if a command fails set -e # abort the script if an unitialized shell variable is used set -u i = 0; while [$i -l 1] do src/meshpro input/martini.off video/noise/image$i.off -noise $i src/meshview video/noise/image$i.off -output_image video/noise/image$i.jpg -exit_immediately i='expr $i + 0.1' done When I try to run the script, I get the following error: line 14: i: command not found. I used a tutorial to apply to my code. Any suggestions on what I'm doing wrong?

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• Ray-box Intersection Theory

  - by Myx

  Hello: I wish to determine the intersection point between a ray and a box. The box is defined by its min 3D coordinate and max 3D coordinate and the ray is defined by its origin and the direction to which it points. Currently, I am forming a plane for each face of the box and I'm intersecting the ray with the plane. If the ray intersects the plane, then I check whether or not the intersection point is actually on the surface of the box. If so, I check whether it is the closest intersection for this ray and I return the closest intersection. The way I check whether the plane-intersection point is on the box surface itself is through a function bool PointOnBoxFace(R3Point point, R3Point corner1, R3Point corner2) { double min_x = min(corner1.X(), corner2.X()); double max_x = max(corner1.X(), corner2.X()); double min_y = min(corner1.Y(), corner2.Y()); double max_y = max(corner1.Y(), corner2.Y()); double min_z = min(corner1.Z(), corner2.Z()); double max_z = max(corner1.Z(), corner2.Z()); if(point.X() >= min_x && point.X() <= max_x && point.Y() >= min_y && point.Y() <= max_y && point.Z() >= min_z && point.Z() <= max_z) return true; return false; } where corner1 is one corner of the rectangle for that box face and corner2 is the opposite corner. My implementation works most of the time but sometimes it gives me the wrong intersection. I was wondering if the way I'm checking whether the intersection point is on the box is correct or if I should use some other algorithm. Thanks.

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• Soft Shadows in Raytracing 3D to 2D

  - by Myx

  Hello: I wish to implement soft shadows produced by area lights in my raytracer. I'm having trouble generating the random samples. So I have a scene in which I have an area light (represented as a circle) whose world (x,y,z) coordinates of the center are given, the radius is given, the normal of the plane on which the circle lies is given, as well as the color and attenuation factors. The sampling scheme I wish to use is the following: generate samples on the quadrilateral that encompasses the circle and discard points outside the circle until the required number of samples within the circle have been found. I'm having trouble understanding how I can transform the 3D coordinates of the center of the circle to its 2D representation (I don't think I can assume that the projection of the circle is on the x-y axis and thus just get rid of the z-component). I think the plane normal information should be used but I'm not sure how. Any and all suggestions are appreciated.

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• Daubechies-4 Transform in MATLAB

  - by Myx

  Hello: I have a 4x4 matrix which I wish to decompose into 4 frequency bands (LL, HL, LH, HH where L=low, H=high) by using a one-level Daubechies-4 wavelet transform. As a result of the transform, each band should contain 2x2 coefficients. How can I do this in MATLAB? I know that MATLAB has dbaux and dbwavf functions. However, I'm not sure how to use them and I also don't have the wavelet toolbox. Any help is greatly appreciated. Thanks.

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• point light illumination using Phong model

  - by Myx

  Hello: I wish to render a scene that contains one box and a point light source using the Phong illumination scheme. The following are the relevant code snippets for my calculation: R3Rgb Phong(R3Scene *scene, R3Ray *ray, R3Intersection *intersection) { R3Rgb radiance; if(intersection->hit == 0) { radiance = scene->background; return radiance; } ... // obtain ambient term ... // this is zero for my test // obtain emissive term ... // this is also zero for my test // for each light in the scene, obtain calculate the diffuse and specular terms R3Rgb intensity_diffuse(0,0,0,1); R3Rgb intensity_specular(0,0,0,1); for(unsigned int i = 0; i < scene->lights.size(); i++) { R3Light *light = scene->Light(i); R3Rgb light_color = LightIntensity(scene->Light(i), intersection->position); R3Vector light_vector = -LightDirection(scene->Light(i), intersection->position); // check if the light is "behind" the surface normal if(normal.Dot(light_vector)<=0) continue; // calculate diffuse reflection if(!Kd.IsBlack()) intensity_diffuse += Kd*normal.Dot(light_vector)*light_color; if(Ks.IsBlack()) continue; // calculate specular reflection ... // this I believe to be irrelevant for the particular test I'm doing } radiance = intensity_diffuse; return radiance; } R3Rgb LightIntensity(R3Light *light, R3Point position) { R3Rgb light_intensity; double distance; double denominator; if(light->type != R3_DIRECTIONAL_LIGHT) { distance = (position-light->position).Length(); denominator = light->constant_attenuation + (light->linear_attenuation*distance) + (light->quadratic_attenuation*distance*distance); } switch(light->type) { ... case R3_POINT_LIGHT: light_intensity = light->color/denominator; break; ... } return light_intensity; } R3Vector LightDirection(R3Light *light, R3Point position) { R3Vector light_direction; switch(light->type) { ... case R3_POINT_LIGHT: light_direction = position - light->position; break; ... } light_direction.Normalize(); return light_direction; } I believe that the error must be somewhere in either LightDirection(...) or LightIntensity(...) functions because when I run my code using a directional light source, I obtain the desired rendered image (thus this leads me to believe that the Phong illumination equation is correct). Also, in Phong(...), when I computed the intensity_diffuse and while debugging, I divided light_color by 10, I was obtaining a resulting image that looked more like what I need. Am I calculating the light_color correctly? Thanks.

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• Ray-Box Intersection during Scene traversal with matrix transforms

  - by Myx

  Hello: There are a few ways that I'm testing my ray-box intersections: Using the ComputeIntersectionBox(...) method, that takes a ray and a box as arguments and computes the closest intersection of the ray and the box. This method works by forming a plane with each of the faces of the box and finding an intersection with each of the planes. Once an intersection is found, a check is made whether or not the point is on the surface of the box by checking that the intersection point is between the corner points. When I look at rays after running this algorithm on two different boxes, I obtain the correct intersections. Using ComputeIntersectionScene(...) method without using the matrix transformations on a scene that has two spheres, a dodecahedron (a triangular mesh), and two boxes. ComputeIntersectionScene(...) recursively traverses all of the nodes of the scene graph and computes the closest intersection with the given ray. This test in particular does not apply any transformations that parent nodes may have that also need to be applied to their children. With this test, I also obtain the correct intersections. Using ComputeIntersectionScene(...) method WITH the matrix transformations. This test works like the one above except that before finding an intersection between the ray and a node in the scene, the ray is transformed into the node's coordinate frame using the inverse of the node's transformation matrix and after the intersection has been computed, this intersection is transformed back into the world coordinates by applying the transformation matrix to the intersection point. When testing with the third method on the same scene file as described in 2, testing with 4 rays (thus one ray intersects the one sphere, one ray the the other sphere, one ray one box, and one ray the other box), only the two spheres get intersected and the two boxes do not get intersections. When I debug looking into my ComputeIntersectionBox(...) method, it actually tells me that the ray intersects every plane on the box but each intersection point does not lie on the box. This seems to be strange behavior, since when using test 2 without transformations, I obtain the correct box intersections (thus, I believe my ray-box intersection to be correct) and when using test 3 WITH transformations, I obtain the correct sphere intersections (thus, I believe my transformed ray should be OK). Any suggestions where I could be going wrong? Thank you in advance.

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• Variable-byte encoding clarification

  - by Myx

  Hello: I am very new to the world of byte encoding so please excuse me (and by all means, correct me) if I am using/expressing simple concepts in the wrong way. I am trying to understand variable-byte encoding. I have read the Wikipedia article (http://en.wikipedia.org/wiki/Variable-width_encoding) as well as a book chapter from an Information Retrieval textbook. I think I understand how to encode a decimal integer. For example, if I wanted to provide variable-byte encoding for the integer 60, I would have the following result: 1 0 1 1 1 1 0 0 (please let me know if the above is incorrect). If I understand the scheme, then I'm not completely sure how the information is compressed. Is it because usually we would use 32 bits to represent an integer, so that representing 60 would result in 1 1 1 1 0 0 preceded by 26 zeros, thus wasting that space as opposed to representing it with just 8 bits instead? Thank you in advance for the clarifications.

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• vim-latex config

  - by Myx

  Hello: I have installed vim-latex package using my ubuntu's synaptic package manager. I followed the instructions here to edit my .vimrc file. However, when I open up a .tex file in vim, nonw of the new menu options appear and I can't seem to compile documents using \ll. What did I do wrong?

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• glui /usr/bin/ld: cannot find -lXmu

  - by Myx

  Hello: I have downloaded the latest GLUI source code and now I am trying to compile it. When I do so, I get the following error: g++ -O0 -Wall -pedantic -I./ -I./include -I/usr/X11R6/include -o bin/example1 example/example1.cpp -L./lib -lglui -L/usr/X11R6/lib/libXdmcp.a -lglut -lGLU -lGL -lXmu -lXext -lX11 -lXi -lm /usr/bin/ld: cannot find -lXmu collect2: ld returned 1 exit status When I did a locate libXmu, I get the following output: > %:~/src/GLUI/src$ locate libXmu > /usr/lib/libXmu.so.6 > /usr/lib/libXmu.so.6.2.0 > /usr/lib/libXmuu.so.1 > /usr/lib/libXmuu.so.1.0.0 Do I get the error because I don't have a /usr/lib/libXmu.so? If this is the case, how can I make one? (I am not experienced with linking at all). Thanks!

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• uniform generation of points on 3D box

  - by Myx

  Hello: I would like to generate random points on a 3D box defined by its (minx, miny, minz) and (maxx, maxy, maxz) corners. I was thinking of generating a random point inside of the box and then somehow projecting it onto one of the box sides. However, I don't have explicit plane information for the box sides and this seems like it will not produce a uniform distribution of points since if some sides of the box are bigger than others, those sides should have more points generated on them. Any suggestions are appreciated. Thanks.

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• uniform generation of 3D points on cylinder/cone

  - by Myx

  Hello: I wish to randomly and uniformly generate points on a cylinder and a cone (separately). The cylinder is defined by its center, its radius and height. Same specifications for the cone. I am able to get the bounding box for each shape so I was thinking of generating points within the bounding box. However, I'm not sure how to project them onto the cylinder/cone or if this is the best idea. Any suggestions? Thanks.

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• OpenGL render vs. own Phong Illumination Implementation

  - by Myx

  Hello: I have implemented a Phong Illumination Scheme using a camera that's centered at (0,0,0) and looking directly at the sphere primitive. The following are the relevant contents of the scene file that is used to view the scene using OpenGL as well as to render the scene using my own implementation: ambient 0 1 0 dir_light 1 1 1 -3 -4 -5 # A red sphere with 0.5 green ambiance, centered at (0,0,0) with radius 1 material 0 0.5 0 1 0 0 1 0 0 0 0 0 0 0 0 10 1 0 sphere 0 0 0 0 1 The resulting image produced by OpenGL. The image that my rendering application produces. As you can see, there are various differences between the two: The specular highlight on my image is smaller than the one in OpenGL. The diffuse surface seems to not diffuse in the correct way, resulting in the yellow region to be unneccessarily large in my image, whereas in OpenGL there's a nice dark green region closer to the bottom of the sphere The color produced by OpenGL is much darker than the one in my image. Those are the most prominent three differences that I see. The following is my implementation of the Phong illumination: R3Rgb Phong(R3Scene *scene, R3Ray *ray, R3Intersection *intersection) { R3Rgb radiance; if(intersection->hit == 0) { radiance = scene->background; return radiance; } R3Vector normal = intersection->normal; R3Rgb Kd = intersection->node->material->kd; R3Rgb Ks = intersection->node->material->ks; // obtain ambient term R3Rgb intensity_ambient = intersection->node->material->ka*scene->ambient; // obtain emissive term R3Rgb intensity_emission = intersection->node->material->emission; // for each light in the scene, obtain calculate the diffuse and specular terms R3Rgb intensity_diffuse(0,0,0,1); R3Rgb intensity_specular(0,0,0,1); for(unsigned int i = 0; i < scene->lights.size(); i++) { R3Light *light = scene->Light(i); R3Rgb light_color = LightIntensity(scene->Light(i), intersection->position); R3Vector light_vector = -LightDirection(scene->Light(i), intersection->position); // calculate diffuse reflection intensity_diffuse += Kd*normal.Dot(light_vector)*light_color; // calculate specular reflection R3Vector reflection_vector = 2.*normal.Dot(light_vector)*normal-light_vector; reflection_vector.Normalize(); R3Vector viewing_vector = ray->Start() - intersection->position; viewing_vector.Normalize(); double n = intersection->node->material->shininess; intensity_specular += Ks*pow(max(0.,viewing_vector.Dot(reflection_vector)),n)*light_color; } radiance = intensity_emission+intensity_ambient+intensity_diffuse+intensity_specular; return radiance; } Here are the related LightIntensity(...) and LightDirection(...) functions: R3Vector LightDirection(R3Light *light, R3Point position) { R3Vector light_direction; switch(light->type) { case R3_DIRECTIONAL_LIGHT: light_direction = light->direction; break; case R3_POINT_LIGHT: light_direction = position-light->position; break; case R3_SPOT_LIGHT: light_direction = position-light->position; break; } light_direction.Normalize(); return light_direction; } R3Rgb LightIntensity(R3Light *light, R3Point position) { R3Rgb light_intensity; double distance; double denominator; if(light->type != R3_DIRECTIONAL_LIGHT) { distance = (position-light->position).Length(); denominator = light->constant_attenuation + light->linear_attenuation*distance + light->quadratic_attenuation*distance*distance; } switch(light->type) { case R3_DIRECTIONAL_LIGHT: light_intensity = light->color; break; case R3_POINT_LIGHT: light_intensity = light->color/denominator; break; case R3_SPOT_LIGHT: R3Vector from_light_to_point = position - light->position; light_intensity = light->color*( pow(light->direction.Dot(from_light_to_point), light->angle_attenuation)); break; } return light_intensity; } I would greatly appreciate any suggestions as to any implementation errors that are apparent. I am wondering if the differences could be occurring simply because of the gamma values used for display by OpenGL and the default gamma value for my display. I also know that OpenGL (or at least tha parts that I was provided) can't cast shadows on objects. Not that this is relevant for the point in question, but it just leads me to wonder if it's simply display and capability differences between OpenGL and what I am trying to do. Thank you for your help.

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• Ray Generation Inconsistency

  - by Myx

  I have written code that generates a ray from the "eye" of the camera to the viewing plane some distance away from the camera's eye: R3Ray ConstructRayThroughPixel(...) { R3Point p; double increments_x = (lr.X() - ul.X())/(double)width; double increments_y = (ul.Y() - lr.Y())/(double)height; p.SetX( ul.X() + ((double)i_pos+0.5)*increments_x ); p.SetY( lr.Y() + ((double)j_pos+0.5)*increments_y ); p.SetZ( lr.Z() ); R3Vector v = p-camera_pos; R3Ray new_ray(camera_pos,v); return new_ray; } ul is the upper left corner of the viewing plane and lr is the lower left corner of the viewing plane. They are defined as follows: R3Point org = scene->camera.eye + scene->camera.towards * radius; R3Vector dx = scene->camera.right * radius * tan(scene->camera.xfov); R3Vector dy = scene->camera.up * radius * tan(scene->camera.yfov); R3Point lr = org + dx - dy; R3Point ul = org - dx + dy; Here, org is the center of the viewing plane with radius being the distance between the viewing plane and the camera eye, dx and dy are the displacements in the x and y directions from the center of the viewing plane. The ConstructRayThroughPixel(...) function works perfectly for a camera whose eye is at (0,0,0). However, when the camera is at some different position, not all needed rays are produced for the image. Any suggestions what could be going wrong? Maybe something wrong with my equations? Thanks for the help.

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• Graphics/Vision Interesting Topics

  - by Myx

  Hello: I would like to do an interesting project for a computer graphics course. I know that there is a lot of literature out there (i.e. SIGGRAPH conference papers). I have a very large range of interest with regard to computer graphics (i.e. image processing, 3D modeling, rendering, animation). However, I've only taken computer vision/graphics for 2 semesters and thus don't have too much background experience, except for the class projects that I had to do. I've been looking through SIGGRAPH papers trying to see if there is anything that will be of interest to me but the literature is extremely vast. I was wondering if anyone has any topic suggestions, anything interesting that you ran across that you could recommend. I would prefer to do something fun yet slightly challenging (not really interested in making a shooter game). If this question does not belong here, I apologize and please let me know where I should move it. Thanks!

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• Different function returns from command line and within function

  - by Myx

  Hello: I have an extremely bizzare situation: I have a function in MATLAB which calls three other main functions and produces two figures for me. The function reads in an input jpeg image, crops it, segments it using kmeans clustering, and outputs 2 figures to the screen - the original image and the clustered image with the cluster centers indicated. Here is the function in MATLAB: function [textured_avg_x photo_avg_x] = process_database_images() clear all warning off %#ok type_num_max = 3; % type is 1='texture', 2='graph', or 3='photo' type_num_max = 1; img_max_num_photo = 100; % 400 photo images img_max_num_other = 100; % 100 textured, and graph images for type_num = 1:2:type_num_max if(type_num == 3) img_num_max = img_max_num_photo; else img_num_max = img_max_num_other; end img_num_max = 1; for img_num = 1:img_num_max [type img] = load_image(type_num, img_num); %img = imread('..\images\445.jpg'); img = crop_image(img); [IDX k block_bounds features] = segment_image(img); end end end The function segment_image first shows me the color image that was passed in, performs kmeans clustering, and outputs the clustered image. When I run this function on a particular image, I get 3 clusters (which is not what I expect to get). When I run the following commands from the MATLAB command prompt: >> img = imread('..\images\texture\1.jpg'); >> img = crop_image(img); >> segment_image(img); then the first image that is displayed by segment_image is the same as when I run the function (so I know that the clustering is done on the same image) but the number of clusters is 16 (which is what I expect). In fact, when I run my process_database_images() function on my entire image database, EVERY image is evaluated to have 3 clusters (this is a problem), whereas when I test some images individually, I get in the range of 12-16 clusters, which is what I prefer and expect. Why is there such a discrepancy? Am I having some syntax bug in my process_database_images() function? If more code is required from me (i.e. segment_images function, or crop_image function), please let me know. Thanks.

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• MATLAB: different function returns from command line and within function

  - by Myx

  Hello: I have an extremely bizzare situation: I have a function in MATLAB which calls three other main functions and produces two figures for me. The function reads in an input jpeg image, crops it, segments it using kmeans clustering, and outputs 2 figures to the screen - the original image and the clustered image with the cluster centers indicated. Here is the function in MATLAB: function [textured_avg_x photo_avg_x] = process_database_images() clear all warning off %#ok type_num_max = 3; % type is 1='texture', 2='graph', or 3='photo' type_num_max = 1; img_max_num_photo = 100; % 400 photo images img_max_num_other = 100; % 100 textured, and graph images for type_num = 1:2:type_num_max if(type_num == 3) img_num_max = img_max_num_photo; else img_num_max = img_max_num_other; end img_num_max = 1; for img_num = 1:img_num_max [type img] = load_image(type_num, img_num); %img = imread('..\images\445.jpg'); img = crop_image(img); [IDX k block_bounds features] = segment_image(img); end end end The function segment_image first shows me the color image that was passed in, performs kmeans clustering, and outputs the clustered image. When I run this function on a particular image, I get 3 clusters (which is not what I expect to get). When I run the following commands from the MATLAB command prompt: >> img = imread('..\images\texture\1.jpg'); >> img = crop_image(img); >> segment_image(img); then the first image that is displayed by segment_image is the same as when I run the function (so I know that the clustering is done on the same image) but the number of clusters is 16 (which is what I expect). In fact, when I run my process_database_images() function on my entire image database, EVERY image is evaluated to have 3 clusters (this is a problem), whereas when I test some images individually, I get in the range of 12-16 clusters, which is what I prefer and expect. Why is there such a discrepancy? Am I having some syntax bug in my process_database_images() function? If more code is required from me (i.e. segment_images function, or crop_image function), please let me know. Thanks.

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• c++ function scope

  - by Myx

  I have a main function in A.cpp which has the following relevant two lines of code: B definition(input_file); definition.Print(); In B.h I have the following relevant lines of code: class B { public: // Constructors B(void); B(const char *filename); ~B(void); // File input int ParseLSFile(const char *filename); // Debugging void Print(void); // Data int var1; double var2; vector<char* > var3; map<char*, vector<char* > > var4; } In B.cpp, I have the following function signatures (sorry for being redundant): B::B(void) : var1(-1), var2(numeric_limits<double>::infinity()) { } B::B(const char *filename) { B *def = new B(); def->ParseLSFile(filename); } B::~B(void) { // Free memory for var3 and var 4 } int B::ParseLSFile(const char *filename) { // assign var1, var2, var3, and var4 values } void B::Print(void) { // print contents of var1, var2, var3, and var4 to stdout } So when I call Print() from within B::ParseLSFile(...), then the contents of my structures print correctly to stdout. However, when I call definition.Print() from A.cpp, my structures are empty or contain garbage. Can anyone recommend the correct way to initialize/pass my structures so that I can access them outside of the scope of my function definition? Thanks.

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• Perturb vector by some angle

  - by Myx

  Hello: I have a unit vector in 3D space whose direction I wish to perturb by some angle within the range 0 to theta, with the position of the vector remaining the same. What is a way I can accomplish this? Thanks.

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• c++ File input/output

  - by Myx

  Hi: I am trying to read from a file using fgets and sscanf. In my file, I have characters on each line of the while which I wish to put into a vector. So far, I have the following: FILE *fp; fp = fopen(filename, "r"); if(!fp) { fprintf(stderr, "Unable to open file %s\n", filename); return 0; } // Read file int line_count = 0; char buffer[1024]; while(fgets(buffer, 1023, fp)) { // Increment line counter line_count++; char *bufferp = buffer; ... while(*bufferp != '\n') { char *tmp; if(sscanf(bufferp, "%c", tmp) != 1) { fprintf(stderr, "Syntax error reading axiom on " "line %d in file %s\n", line_count, filename); return 0; } axiom.push_back(tmp); printf("put %s in axiom vector\n", axiom[axiom.size()-1]); // increment buffer pointer bufferp++; } } my axiom vector is defined as vector<char *> axiom;. When I run my program, I get a seg fault. It happens when I do the sscanf. Any suggestions on what I'm doing wrong?

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• MATLAB: draw centroids

  - by Myx

  Hello - my main question is given a feature centroid, how can I draw it in MATLAB? In more detail, I have an NxNx3 image (an rgb image) of which I take 4x4 blocks and compute a 6-dimensional feature vector for each block. I store these feature vectors in an Mx6 matrix on which I run kmeans function and obtain the centroids in a kx6 matrix, where k is the number of clusters and 6 is the number of features for each block. How can I draw these center clusters in my image in order to visualize if the algorithm is performing the way I wish it to perform? Or if anyone has any other way/suggestions on how I can visualize the centroids on my image, I'd greatly appreciate it. Thank you.

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