matrix

问题 I am using mkl cblas_dgemm and currently have it with CblasRowMajor , CblasNoTrans , CblasNotrans , for my matrices. I know that c is a row major language, whereas dgemm is a column major algorithm. I am interested to know if switching the ordering of the matrices will have any affect on the cblas_dgemm algorithm if I am linking against mkl . Is mkl smart enough to do things behind the scenes that I would try to do to optimized the matrix multiplcations? If not, what is the best way to

问题 I've got coordinates of 4 points in 2D that form a rectangle and their coordinates after a perspective transformation has been applied. The perspective transformation is calculated in homogeneous coordinates and defined by a 3x3 matrix M . If the matrix is not known, how can I calculate it from the given points? The calculation for one point would be: | M11 M12 M13 | | P1.x | | w*P1'.x | | M21 M22 M23 | * | P1.y | = | w*P1'.y | | M31 M32 M33 | | 1 | | w*1 | To calculate all points

问题 I need help writing a method to find out a sum of 2 different sized 2d arrays. public static int[][] summary(int[][] tab1, int[][] tab2, int x) { int[][] finalTab = new int[4][5]; // I took sizes of bigger one if (x < 0) { for (int i = 0; i < finalTab.length - 1; i++) { for (int j = 0; j < finalTab[i].length - 1; j++) { finalTab[i][j] = tab1[i][j] + tab2[i][j]; if (tab1[i][j] == 0) { finalTab[i][j] = tab2[i][j]; } } } for (int i = 0; i < finalTab.length; i++) { for (int j = 0; j < finalTab[i]

问题 I need help writing a method to find out a sum of 2 different sized 2d arrays. public static int[][] summary(int[][] tab1, int[][] tab2, int x) { int[][] finalTab = new int[4][5]; // I took sizes of bigger one if (x < 0) { for (int i = 0; i < finalTab.length - 1; i++) { for (int j = 0; j < finalTab[i].length - 1; j++) { finalTab[i][j] = tab1[i][j] + tab2[i][j]; if (tab1[i][j] == 0) { finalTab[i][j] = tab2[i][j]; } } } for (int i = 0; i < finalTab.length; i++) { for (int j = 0; j < finalTab[i]

问题 I need help writing a method to find out a sum of 2 different sized 2d arrays. public static int[][] summary(int[][] tab1, int[][] tab2, int x) { int[][] finalTab = new int[4][5]; // I took sizes of bigger one if (x < 0) { for (int i = 0; i < finalTab.length - 1; i++) { for (int j = 0; j < finalTab[i].length - 1; j++) { finalTab[i][j] = tab1[i][j] + tab2[i][j]; if (tab1[i][j] == 0) { finalTab[i][j] = tab2[i][j]; } } } for (int i = 0; i < finalTab.length; i++) { for (int j = 0; j < finalTab[i]

问题 I need help writing a method to find out a sum of 2 different sized 2d arrays. public static int[][] summary(int[][] tab1, int[][] tab2, int x) { int[][] finalTab = new int[4][5]; // I took sizes of bigger one if (x < 0) { for (int i = 0; i < finalTab.length - 1; i++) { for (int j = 0; j < finalTab[i].length - 1; j++) { finalTab[i][j] = tab1[i][j] + tab2[i][j]; if (tab1[i][j] == 0) { finalTab[i][j] = tab2[i][j]; } } } for (int i = 0; i < finalTab.length; i++) { for (int j = 0; j < finalTab[i]

问题 This question already has an answer here : How to subset matrix to one column, maintain matrix data type, maintain row/column names? (1 answer) Closed 5 years ago . When I try to subset a 1-colum matrix by it's row names the subsetting works but an numeric vector is returned. can you somehow prevent that behaviour and keep the row names? M<-as.matrix(rnorm(5)) rownames(M)<-LETTERS[1:5] M [,1] A 0.6250957 B 0.7330598 C -0.7127075 D 0.2162602 E 0.2223444 M <- M[which(rownames(M) != "A")] M ##

问题 I'm trying to go over the problems in the Cracking the Coding Interview book. One of the questions asks me to rotate a matrix 90 degrees clockwise. Now, while trying to solidify my understanding of matrix rotation, I tried to embark on a new problem: to try to rotate a matrix 90 degrees counterclockwise (the other direction). I've tried to go through layers of a square matrix, the outer layer, iterating all the way into the inner layer and rotating all the indexes of each side of the "square"

问题 I am maximizing a likelihood function and trying to reduce the loop. I want to add the vector(parameters to be estimated) to all rows of a matrix (data). The length of vector equals to the column of matrix. a+b would give the wrong results because the recycle rule of R is by column not row. a<-c(1,2,0,0,0) # parameters to be optimized b<-matrix(1,ncol=5,nrow=6) # data t(a+t(b)) # my code would work, anything more intuitive? Desired output [,1] [,2] [,3] [,4] [,5] [1,] 2 3 1 1 1 [2,] 2 3 1 1 1

问题 I am maximizing a likelihood function and trying to reduce the loop. I want to add the vector(parameters to be estimated) to all rows of a matrix (data). The length of vector equals to the column of matrix. a+b would give the wrong results because the recycle rule of R is by column not row. a<-c(1,2,0,0,0) # parameters to be optimized b<-matrix(1,ncol=5,nrow=6) # data t(a+t(b)) # my code would work, anything more intuitive? Desired output [,1] [,2] [,3] [,4] [,5] [1,] 2 3 1 1 1 [2,] 2 3 1 1 1