How to build nested array of 1x3 vectors in the (n,m) posision of 2D matrix in a for loop? And then how to access the n,m vector ? Is there a better way than below. for n =1:2 for m =1:3 v = [n,m,n]' % test vector to be stored...

My question is in regard of the following phrase from the book: Unfortunately, the SoA form is not ideal in all circumstances. For random or incoherent circumstances, gathers are used to access the data and the SoA form can result in extra unneeded data being read into cache, thus reducing...

I have many expressions that look like auto result = vec3f.cwiseProduct( vec3ui ); where vec3f is from type Eigen::Matrix< float, 3, 1 > and vec3ui is from Eigen::Matrix< unsigned int, 3, 1 >. These doesn't seem to be allowed, at least the compiler complains about it. Hence I need to...

A reproducible example of the code I'm trying vectorise. cutOffs <- seq(1,10,0.2) plotOutput <- matrix(nrow=length(cutOffs), ncol=2) colnames(plotOutput) <- c("x","y") plotOutput[,"y"] <- cutOffs for(plotPoint in 1:length(cutOffs)) { plotOutput[plotPoint, "x"] <- nrow(iris[ which(iris$Sepal.Length > cutOffs[plotPoint] & iris$Sepal.Width > cutOffs[plotPoint]), ]) } plotOutput Specifically what I'm looking to find out is, if there's...

I have a struct like this temp_struct(1).budget=8 temp_struct(2).budget=8 and I want to subtract a constant value from both of them (replacing 8 with the new value). How can i do it more efficiently without using a loop in matlab?...

I'm looking for a library/tool/image processing technique which can create vectors out of images (similar to text vectorization like TFIDF or so). Can anybody share some ideas how to proceed?

I have stumbled upon an interesting case of comparing (==, !=) float types. I encountered this problem while porting my own software from windows to linux. It's a bit of a bummer. The relevant code is the following: template<class T> class PCMVector2 { public: T x, y; public: bool operator...

I'm trying to get my head around the amazing list processing abilities of python (And eventually numpy). I'm converting some C code I wrote to python. I have a text datafile where first row is a header, and then every odd row is my input data and every even row...

I am trying to combine vectorization and recursion in this implementation of the factorial function: fac <- function(n) { ifelse(n == 1, 1, n * fac(n-1)) } fac(6) #720 fac(c(6,7)) #Error: evaluation nested too deeply: infinite recursion / options(expressions=)? #Error during wrapup: evaluation nested too deeply: infinite recursion / options(expressions=)?...

I want to create a matrix from all combinations of elements of one vector that fulfill a condition For example, I have this vector a = [1 2 3 4 5] and want to create a matrix like a = [1 0 0 0 0; 1 2 0 0 0;...

Let i = [1 2] and j = [3 5]. Now in octave: arrayfun(@(x,y) x+y,i,j) we get [4 7]. But I want to apply the function on the combinations of i vs. j to get [i(1)+j(1) i(1)+j(2) i(2)+j(1) i(2)+j(2)]=[4 6 5 7]. How do I accomplish this? I know I...

Looking for a fast vectorized function that returns the rolling number of consecutive non-zero values. The count should start over at 0 whenever encountering a zero. The result should have the same shape as the input array. Given an array like this: x = np.array([2.3, 1.2, 4.1 , 0.0, 0.0,...

My situation: I have a long (20k lines) list of URLs that I need to scrape particular data elements from for an analysis. For the purpose of this example, I'm looking for a particular field called "sol-num", which the the solicitation number. Using the following function, I can fetch the...

I have a matrix J of size (j,v) and a vector JTildeIDX of size v. The vector contains the start for a cumsum operation over J. That is, given >>> JTildeIDX array([0, 0, 9, 9, 9]) >>> J array([[ 1. , 1. , 1. , 1. , 1. ], [...

I might be a bit rusty with Matlab, maybe the answer to this question is more trivial than I imagine at this moment. However I have searched online for efficient solutions and I haven't found any, so I will try here. I have a large matrix, something like y here:...

So I have one matrix containing the data and a vector containing information on which data I should extract from the matrix. The real matrix is much longer but below is a short version just to illustrate what I meant. Data matrix = array([[1 2 3],[0 3 5],[1 4 4]])...

How can I define a matrix M according to M=[a:(b-a)/5:b] (from a to b in 5 steps), when a and b are vectors or sets; more specifically, each row i in M should have a first value equal to a(i) and last value b(i) and, in between, 5 equal steps....

I am trying to use Numpy and vectorization operations to make a section of code run faster but I don't succeed to find a solution. If somebody has an idea... Thanks. Here's the working code with loops: y = np.zeros(len(tab)) for i in range(len(tab)): s = 0 for n in...

I'm trying to build a constraint matrix that I'm going to use with linprog, and I'm struggling to build it efficiently without using for loops. Here is an example of what I'm trying to achieve: A = zeros(3, 3); % Constraint matrix i = [1 3]; % row indexes j...

Say I have two arrays, import numpy as np x = np.array([1, 2, 3, 4]) y = np.array([5, 6, 7, 8]) What's the fastest, most Pythonic, etc., etc. way to get a new array, z, with a number of elements equal to x.size * y.size, in which the elements are...

I basically want to vectorize the following: vect_y = zeros(1,numel(vect_x); for i = 1:numel(vect_x) vect_y = sum(vect_x(1:i)); end Is this possible? As an example, I was trying to use arrayfun the following way: y = arrayfun(@(y) sum(y), vect_x(1:1), vect_x(1:2), ..., vect_x(1:n)); But this won't work and it's not clean. edit:...

I did search SO but didn't find for using something like MPICH or vectorization. In fortran, I'd use MPICH to break up the code to paralyze. This is to run on an iPad with Metal available. I have a 1-D string array with many hundred of thousands of elements, many...

Setup Given a 2D array, I would like to create a 3D array where the values along the third dimension at (i.e. stacked[row, col, :]) are the flattened neighbors of the original array at [row, col]. I would like to generalize this process to handle an arbitrary (but reasonable) search...

Say I have a Numpy vector, A = zeros(100) and I divide it into subvectors by a list of breakpoints which index into A, for instance, breaks = linspace(0, 100, 11, dtype=int) So the i-th subvector would be lie between the indices breaks[i] (inclusive) and breaks[i+1] (exclusive). The breaks are...

I'm having a vectorization problem. Say I'm having a vector x <- c(0,0,1,0,1,1,0) , what I want is to get the vector (1,0,1,1), or to remove all the 0s from the first spot to the first non-zero spot and all the 0s from last non-zero spot to the last spot....

I have a numpy array with shape a.shape = (1,k*d)and i want to transform it to a numpy array with shape b.shape = (k*d,k) in each column b[i,j] = a[i] if j<i+1 b[i,j] = 0 if not for example: k = 3 d= 2 ********** A = |a| => B...

NLopt is a solver for optimization, which implements different optimization algorithms and is implemented in different languages. In order to use the LD_LBFGS algorithm in Julia, does the variable have to be a vector as opposed to a matrix? If yes, once we need to optimize an objective which is...

In a route planning algorithm, I'm trying to perform a filter on a list of nodes based on distance to another node. I'm actually pulling the lists from a crude scene graph. I use the term "cell" to refer to a volume within a simple scenegraph from which we've fetched...

I'm porting some code from R to julia to get familiar with the language, and I found a few patterns that don't translate smoothly. Consider the following function, # Ricatti-Bessel and derivatives up to nmax, vectorised over x function rb(x, nmax) n = 1:nmax nu = 0.5 + [0, n]...

I have data.frame sent with sentences in sent$words and dictionary with pos/neg words in wordsDF data frame (wordsDF[x,1]). Positive words = 1 and negative = -1 (wordsDF[x,2]). The words in that wordsDF data frame are sorted in decreasing order according to their length (length of string). I used this purpose...

I want to project the texture of 3D surface (CylCoors 300000x3) into a 2D plane (Image 380x360). For doing so I take every unique value in Z (UniqueZ=unique(CylCoors(:,3))) and and Theta (UniqueTheta=unique(CylCoors(:,1))) and project all the texture values (PointValues 300000x1) where both meet like this: Image=zeros(max(UniqueH),max(UniqueTheta)); %380x360 tic HMat=bsxfun(@eq,CylCoors(:,3),UniqueH'); %...

I'd like to replace a specific number of elements of my cell to zero without using for. For example to replace elements of row 2 in example cell a below: How should I proceed possibly using cellfun? a=cell(2,3); cellfun(@(x)(zeros(a{x}(2,:))),a); It gives the error "Bad cell reference operation". what if I'd...

I ran into an operation I cannot seem to achieve via vectorization. Let's say I want to find the matrix of the application defined by h: X -> cross(V,X) where V is a predetermined vector (both X and V are 3-by-1 vectors). In Matlab, I would do something like M=...

I would like to increase the speed of my for loop via vectorization or using Data.table or something else. I have to run the code on 1,000,000 rows and my code is really slow. The code is fairly self-explanatory. I have included an explanation below just in case. I have...

Example: require(data.table) example = matrix(c(rnorm(15, 5, 1), rep(1:3, each=5)), ncol = 2, nrow = 15) example = data.table(example) setnames(example, old=c("V1","V2"), new=c("target", "index")) example threshold = 100 accumulating_cost = function(x,y) { x-cumsum(y) } whats_left = accumulating_cost(threshold, example$target) whats_left I want whats_left to consist of the difference between threshold and the cumulative...

I have a long 1D array. I'd like to create an array that is the result of np.arange() applied to each value in the array plus some constant. E.g if the constant = 3 and my array looks like [1,2,3,4,5] I'd like to get [[1,2,3] [2,3,4] [3,4,5] [4,5,6] [5,6,7]] np.arange()...

Mapply applies a 2-dimensional function to the 1st elements of each m-dimensional vector, and then to the 2nd elements of each, etc. The result is an m-dimensional vector. For example > mapply(sum, 1:5, 12:16) [1] 13 15 17 19 21 Now, is there a DIRECT alternative to mapply that applies...

I have three vectors X, Y and Z of equal length n. I need to create an n x n x n array of a function f(X[i],Y[j],Z[k]). The straightforward way to do this is to sequentially loop through each element of each of the 3 vectors. However, the time required...

I have huge dataset of time series which are represented as vectors (no time labels available), due to some errors in measuring process their lengths (as values from length() show) varies slightly (~10%) but each of them definitively describs time interval of exacly two minutes. I would like to rescale/resize...

I'm trying to reshape a multidimensional array into the original image. I have split an image of 512x512 pixels in sub-matrices of 8x8 pixels using the great solution that I found in this question: sub_images = permute(reshape(permute(reshape(i_image, size(i_image, 1), n, []), [2 1 3]), n, m, []), [2 1 3]);...

I've got a dataframe that includes columns like the one on the right here: lengthArray speed_max 1 4 24, 18, 24, 18 2 10 2, 2, 2, 2, 2, 2, 2, 2, 2, 2 3 4 -999, -999, -999, -999 4 2 -999, -999 5 2 18, 18 6 1...

I am converting a MATLAB script into R and regretting it so far, as it is slower at the moment. I'm trying to use "vectorized functions" as much as possible, but I'm relatively new to R and do not know what is meant by this. From my research for loops...

i am trying to learn how to vectorise matlab loops, so im just doing a few small examples. here is the standard loop i am trying to vectorise: function output = moving_avg(input, N) output = []; for n = N:length(input) % iterate over y vector summation = 0; for ii...

How is it possible to create in a vectorized way, in Matlab, a sequence if I've the 2 vectors of startings and ending of the subsequences ? Example Input: A=[12 20 34] B=[18 25 37] I want to get C=[12 13 14 15 16 17 18 20 21 22 23...

The name of this question does not do it justice. This is best explained by numerical example. Let's say I have the following portfolio data, called data. > data Stdev AvgReturn 1 1.92 0.35 2 1.53 0.34 3 1.39 0.31 4 1.74 0.31 5 1.16 0.30 6 1.27 0.29 7...

Suppose (small numbers in this example) I have an array that is 3 x 14 x 5 call this set.seed(1) dfarray=array(rnorm(5*3*14,0,1),dim=c(3,14,5)) I have a matrix that corresponds to this and is 39 (which is 13*3) x 14 Call this matrix: dfmat = matrix(rnorm(13*3*14,0,1),39,14) dfmat = cbind(dfmat,rep(1:3,13)) dfmat = dfmat[order(dfmat [,15]),]...

I need a fast way in Matlab to do something like this (I am dealing with huge vectors, so a normal loop takes forever!): from a vector like [0 0 2 3 0 0 0 5 0 0 7 0] I need to get this: [NaN NaN 2 3 3...

sorry again for multiple silly questions in a day. I am very novice and do not know programming well. I have asked a simple question about for loop here, which has been sorted out: How to divide two different array in for loop matlab I need to initiate this for...

I have some signals. They are all the same length (N = 1024). I have to break each into Ns = 7 segments with L = 256 points so there will be 50% overlapping. S = randi(10,[4 N]); can be thought as 4 signals. I was thinking about saving the...

I need to solve a system of linear equations Lx=b, where x is always a vector (3x1 array), L is an Nx3 array, and b is an Nx1 vector. N usually ranges from 4 to something like 10. I have no problems solving this using scipy.linalg.lstsq(L,b) However, I need to...

Suppose I have an array of the shape (m,n,3), where m and n refers to the y and x coordinates of a point, and the 3 numbers in each point refer to a three-dimensional vector. (A similar situation is an image with height m and width n, and 3 refers...

I have a1 a2 a3. They are constants. I have a matrix A. What I want to do is to get a1*A, a2*A, a3*A three matrices. Then I want transfer them into a diagonal block matrix. For three constants case, this is easy. I can let b1 = a1*A, b2=a2*A,...

I've written a simulation function in R. I'd like to do num simulations. Rather than using a for loop, I'm trying to use some sort of apply function, such as lapply or parallel::mclapply. lapply, as I'm currently using it, is failing. For example: # t1() is a generic example function...

How can I vectorize this loop ? Let b = real array of size (2,3) M = real array of size (7,2) y = real array of size (n,3) b and M are constant and n is "big" (in my problem, n > 80000). I want to optimize (vectorize) this...

We all know that appending a vector to a vector within a for loop in R is a bad thing because it costs time. A solution would be to do it in a vectorized style. Here is a nice example by Joshua Ulrich. It is important to first create a...

I found on Stack a function who solve my problem but right now I would like to speed up my code because I have a lot of list to split. I heard that vectorize a function ca be a solution so tried to vectorize my function with numpy but it...

How do I construct a vector of values from nth column of some data frame, where n is a per-row value defined in some vector? Example: > df <- data.frame(a=c(100, 110, 120, 130, 140), b=c(200, 210, 220, 230, 240), c=c(300, 310, 320, 330, 340)) > df a b c 1...

I have the following lines of code y = zeros(n, 1); for i=1:n b = L * [u(i:-1:max(1,i-M+1));zeros((-i+M)*(i-M<0),1)]; y(i) = b' * gamma; end u is nx1, gamma is Mx1 and L is MxM n takes very large values, so are there any ideas on how to vectorize the for...

So I just answered a question and as soon as it was answered (correctly I think), the questioner deleted it. So here it is again: I am new to R and need help getting this function to work. I need to create a function that can find the log of...

I have a 2D numpy array where column 0 is the pan rotation of a device and column 1 is the tilt rotation. Each row is a different fixture. I want to run the following logic on each row: if(pantilt[0] > 90): pantilt[0] -=180 pantilt[1] *= -1 elif pantilt[0] <...

In matlab, I have a loop of the form: a=1; for (i = 1:N) a = a * b(i) + c(i); end Can this loop be vectorized, or partially unrolled?...

Suppose I have an MxNx3 array A, where the first two indexes refer to the coordinates a point, and the last index (the number '3') refers to the three components of a vector. e.g. A[4,7,:] = [1,2,3] means that the vector at point (7,4) is (1,2,3). Now I need to...

I need to compute in numpy where $x_i$ and $x_j$ are rows in a matrix $X$. Now I am using loop, which is very slow. Is there any numpy native function allows such computation, like einsum: n=X.shape[0] Y=np.zeros((n,n)) for i in range(n): x=(X-X[i])**2 x=np.sum(x, axis=1) Y[i]=x return Y BTW, I...

I'd like to create a 4x12 matrix which is very similar to a upper triangle matrix, it looks like this: 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0...

I am struggling with the problem of optimizing my cython code in order to improve its speed as much as possible. One of the challenges that I could not still figure out how it should be done in cython is mapping an array on a function like what is done...

I have the following optimization problem. Given two np.arrays X,Y and a function K I would like to compute as fast as possible the matrix incidence gram_matrix where the (i,j)-th element is computed as K(X[i],Y[j]). Here there an implementation using nested for-loops, which are acknowledged to be the slowest to...

I am trying to optimize this piece of code and get rid of the nested loop implemented. I am finding difficulties in applying a matrix to pdist function For example, 1+j // -1+j // -1+j // -1-j are the initial points and i am trying to detect 0.5+0.7j to with...

let us consider following code for impulse function function y=impulse_function(n); y=0; if n==0 y=1; end end this code >> n=-2:2; >> i=1:length(n); >> f(i)=impulse_function(n(i)); >> returns result f f = 0 0 0 0 0 while this code >> n=-2:2; >> for i=1:length(n); f(i)=impulse_function(n(i)); end >> f f = 0...

I have a 3D (x,y,nframes) matrix/ movie ( named ch), and a logical mask (x,y). I want to do the mean of the mask pixels in each frame , at the end I get a vector of dim 1xnframes. And I want to do it with the reshape instead than...

I have a 3 for loops and I would like if possible to vectorize the two inner loops. for t=1:size(datesdaily1) for i=1:size(secids,1) sum=0; if inc(t,i)==1 for j=1:size(secids,1) if inc(t,j)==1 sum=sum+weig1(t,j)*sqrt(Rates(t,j))*rhoneutral(i,j); end end b(t,i)=sqrt(Rates(t,i))*sum/MRates(t,1); end end end Any idea on how to accomplish that? Here 'weig', 'inc' and 'Rates' are (size(datesdaily1)...

I would like to create an SSE register with values that I can store in an array of integers, from another SSE register which contains flags 0xFFFF and zeros. For example: __m128i regComp = _mm_cmpgt_epi16(regA, regB); For the sake of argument, lets assume that regComp was loaded with { 0,...

I have 2 functions for determining pi numerically in Julia. The second function (which I think is vectorized) is slower than the first. Why is vectorization slower? Are there rules when to vectorize and when not to? function determine_pi(n) area = zeros(Float64, n); sum = 0; for i=1:n if ((rand()^2+rand()^2)...

Say you have the following array of shape (5, 4, 3): x = array([[[ 0, 2, 1], [ 3, 4, 0], [ 8, 0, 6], [ 9, 0, 0]], [[12, 0, -14], [ 0, 16, 17], [ 0, -19, 20], [21, 22, 0]], [[24, 0, 26], [27, 0, 29], [...

I need to perform in MATLAB the following calculation: where w and v are vectors with N elements and A is a four-dimensional matrix (N^4 elements). This can be achieved by the following pedantic code: N=10; A=rand(N,N,N,N); v=rand(N,1); w=zeros(N,1); for pp=1:N for ll=1:N for mm=1:N for nn=1:N w(pp)=w(pp)+A(pp,ll,mm,nn)*v(ll)*v(mm)*conj(v(nn)); end end...

and thanks in advance for the help. Using Python (mostly numpy), I am trying to compute an upper-triangular matrix where each row "j" is the first j-terms of a geometric series, all rows using the same parameter. For example, if my parameter is B (where abs(B)=<1, i.e. B in [-1,1]),...

How to vectorize this MATLAB function: function [win,vec] = createwin(data,shift,regions,threshold) % % data ... 1D data array % shift ... positive integer scalar % regions ... integer index vector % threshold ... integer scalar % win = zeros(length(data),2*shift+1); for i = 1+shift:length(data)-shift win(i,:) = data(i-shift:i+shift); end vec = false(size(data)); for...

I have a N-dimensional array (Named A). For each row of the first axis of A, I want to obtain the coordinates of the maximum value along the other axes of A. Then I would return a 2-dimensional array with the coordinates of the maximum value for each row of...

Suppose the convolution of a general number of discrete probability density functions needs to be calculated. For the example below there are four distributions which take on values 0,1,2 with the specified probabilities: import numpy as np pdfs = np.array([[0.6,0.3,0.1],[0.5,0.4,0.1],[0.3,0.7,0.0],[1.0,0.0,0.0]]) The convolution can be found like this: pdf = pdfs[0]...

I wish to plot the heat map of a bivariate (independent) Gaussian. To plot it over a 2D square, I did joint_pdf = @(m, s) normpdf(m, 1, 1)*normpdf(s, 1, 1); [x, y] = meshgrid(0:0.1:10, 0:0.1:10); prob_map = zeros(numel(x), numel(y)); for idx1 = 1:size(prob_map, 1) for idx2 = 1:size(prob_map, 2) prob_map(idx1,...

I would like to vectorize the sum of products hereafter in order to speed up my Matlab code. Would it be possible? for i=1:N A=A+hazard(i)*Z(i,:)'*Z(i,:); end where hazard is a vector (N x 1) and Z is a matrix (N x p). Thanks!...

I'm wondering whether there is any compiler (gcc, xlc, etc.) on Power8 that supports OpenMP SIMD constructs on Power8? I tried with XL (13.1) but I couldn't compile successfully. Probably it doesn't support simd construct yet. I could compile with gcc 4.9.1 (with these flags -fopenmp -fopenmp-simd and -O1). I...

This is what my data frame looks like: Name EventType EventDate SalesAmount RunningTotal Runningtotal(prior365Days) John Email 1/1/2014 0 0 0 John Sale 2/1/2014 10 10 10 John Sale 7/1/2014 20 30 30 John Sale 4/1/2015 30 60 50 John Webinar 5/1/2015 0 60 50 Tom Email 1/1/2014 0 0 0...

I am writing an Octave script to calculate the price of an European option. The first part uses Monte Carlo to simulate the underlying asset price over n number of time periods. This is repeated nIter number of times. Octave makes it very easy to setup initial matrices. But I...

I would like to implement a function that works like the numpy.sum function on arrays as on expects, e.g. np.sum([2,3],1) = [3,4] and np.sum([1,2],[3,4]) = [4,6]. Yet a trivial test implementation already behaves somehow awkward: import numpy as np def triv(a, b): return a, b triv_vec = np.vectorize(fun, otypes =...

I have an issue regarding the dtype of the returned numpy array of a vectorized function. My function returns a number, eventually a fraction. Strangely the position of the fraction seems to influence the returned dtype. I want the type always to be object if the function returns a fraction....

Given two vectors X and Y of length n, representing points on the plane, and a neighborhood radius rad, is there a vectorized way to compute the neighborhood matrix of the points? In other words, can the following (painfully slow for large n) loop be vectorized: neighborhood_mat = zeros(n, n);...

I have the following MATLAB code : meanv = [rmean,gmean,bmean]; for i = 1:1:image_info.Height for j = 1:1:image_info.Width % for every pixel x = image_rgb(i,j,1:3); pix_color = [x(:,:,1),x(:,:,2),x(:,:,3)]; d = dist(meanv,pix_color'); if d <= threshold S(i,j) = 1; end end end The above fragment is part of a program that,...

index = [10 100 1000 10000 100000] Let's say I wanted to generate 10, 100,...,100000 (corresponding to index above) exponential random variables with parameter 1/10. I of course did this with a for loop and with the command for example x = exprnd(0.1,100,1) One can also generate the exponential random...

I would like to create a matrix using a list whose elements would be the elements of the matrix under the diagonal. import numpy as np x1 = np.array([0.9375, 0.75, 0.4375, 0.0, 0.9375, 0.75, 0.4375, 0.9375, 0.75, 0.9375]) x1 the matrix I would like to have is array([[ 1. ,...

Lets say we have an Array A = ones(2, 2, 2) and another matrix P = rand(4). I am wondering if it is possible to write the code temp = A(:, :, 1); X = P * temp(:); into one line of code to save the memory consumed by temp....

Lets say i have a matrix, x=[1,2,3,5,4,6,6,7,4,2,3,4,5,6,10,12,4,5,43,23,45,34,54,78]; Now, I want to create a new matrix where i want to know the indices and values, of elements whose value is higher than (not equal to but strictly larger than) all the previous ones. so, the array i am looking for is,...

I want to replace value of n-th column of a matrix, based on a vector values, in a vectorized way. Input: [0 0 0 0] [0 0 0 0] [0 0 0 0] [0 0 0 0] Vector: [2] [4] [1] [3] Expected output: [0 1 0 0] [0 0...

I have a Nx2x2x2 array called A. I also have a Nx2 array called B, which tells me the position of the last two dimensions of A in which I am interested. I am currently getting a Nx2 array, either by using a loop (as in C in the code...

I am struggling with vectorizing this parfor loop. I want to completely remove the parfor loop from the code as it is taking a long time to execute when n is large. Please see the code pasted below. I will appreciate any tips/advice/help any person in this forum can give...

I have a small piecewise function that profiling reveals is taking 60% of the runtime of the program. It is called very often because it goes within some integrals that I perform quite a lot in my code. According to profiling, it is called 213560 times, taking 47.786 s in...

In a previous question, a user asked about iterating over a cell array of anonymous functions. I am wondering whether there is a way to evaluate a set of functions without the explicit use of a for loop. As an example, the following code creates an array of (simple) functions,...

I am going through a really hard time vectorizing the below code, unfortunately you need to look over it to understand what is going on. In gist, this function compares a set of data rows and creates a matrix of comparison relations. The two nested loops calls the inner function...

In Matlab, If I have a 3d matrix as following, I want to know the mean of the regions that have values greater than 5 in each slice. How can I use logical index to do this, with no loops please? I would like to end up with an array...

Given this vector a = [1 2 3 4] I want to create a matrix like this b = [1 0 0 0; 2 1 0 0; 3 2 1 0; 4 3 2 1; 0 4 3 2; 0 0 4 3; 0 0 0 4] in a vectorized...

Yes I know, there have been a number of questions (see this one, for example) regarding the usage of & vs. && in R, but I have not found one that specifically answers my question. As I understand the differences, & does element-wise, vectorised comparison, much like the other arithmetic...