similar to: analytic solution for equation

i am trying to solve a partial differential equation analytically(PDE) in R . i have found some functions that do the stuff numerically. But that will not meet my purpose. is there any function to solve PDE analytically. please help. -- View this message in context: http://r.789695.n4.nabble.com/analytical-solution-of-partial-differential-equation-tp4291618p4291618.html Sent from the R help

Dear R Users, I'm trying to find function that allow me to solve one nonlinear equation. Functions that I found are good for optimization problems. Any suggestions are welcome, rob

>From time to time people request symbolic computations beyond what D() and deriv() etc can provide. A brief look at the internet shows that there are many more or less developed computer algebra packages freely available. Therefore, I wondered if it would be an idea to try to 'integrate' one of these packages in R, which I guess can be done in more or less elegant ways... I do not know

Hello list, Sorry, these questions are not directly linked to R. If I consider an indefinte real matrix, I would like to know if the symmetry of the matrix is sufficient to say that their eigenvectors are real ? And what is the conditions to ensure that eigenvectors are real in the case of an asymmetric matrix (if some conditions exist)? Thanks in Advance, St?phane DRAY

Hello List, I would like to orthonormalize vectors contained in a matrix X taking into account row weights (matrix diagonal D). ie, I want to obtain Z=XA with t(Z)%*%D%*%Z=diag(1) I can do the Gram-Schmidt orthogonalization with subsequent weighted regressions. I know that in the case of uniform weights, qr can do the trick. I wonder if there is a way to do it in the case of non uniform

Hello, suppose I have a list with matrices: a=list(x1=matrix(rnorm(10),5,2),x2=matrix(rnorm(10),5,2),x3=matrix(rnorm(10),5,2)) I want to compute for all combination of xi and xj (x1,x2 x1,x3 and x2,x3) a value. This value is given for the pair x1,x2 by trace(x1%*%t(x1)%*%x2%*%t(x2)) / trace(x1%*%t(x1))*trace(x2%*%t(x2)) I know that product matrices t(xi)%*%xi can be obtained by:

Hello list, I have a problem ... and do not know how to solve it. I would like create a function that estimate the quality of the fit of different functions with different values of parameters. This problem is related to the following one: I would like to create a function "evaluatemyfunction" which evaluate a function f for different values of parameters. For instance, if

Hello list, I have two vectors x and x2: x=runif(10) x2=runif(10) and one vectors with their names : my.names=c("x","x2") I would like to cbind these two vectors using their names contained in the vector my.names. I can create a string with comma ncomma=paste(my.names,collapse=",") and now, I just need a function to transform this string into a adequate

Hello list, I have used scan function to import data into R. I have done some analysis and find strange results. I have found my problem : when importing data with scan, this can slightly modify the data : > write(c(0.251,3.399,-0.481,0.266),"essai.txt") > scan("essai.txt") Read 4 items [1] 0.251 3.399 -0.481 0.266 > print(scan("essai.txt"),17) Read

Hello list, I have 3 matrices with same dimension : > veca=matrix(1:25,5,5) > vecb=matrix(letters[1:25],5,5) > vecc=matrix(LETTERS[1:25],5,5) I would like to obtain a new matrix composed by alternating rows of these different matrices (row 1 of mat 1, row 1 of mat 2, row 1 of mat 3, row 2 of mat 1.....) I have found a solution to do it but it is not very pretty and I wonder if I

Hello, I have a question that is not directly related to R ... but I try to do it in R ;-) : I would like to generate a matrix Q satisfying (for a given Z, X and W) the two following conditions: t(Q)%*%Q=Z (1) XQ=W (2) where: Q is m rows and r columns X is p rows and m columns D is p rows and r columns C is r rows and r columns with m>p,r e.g: m=6, p=2 r=3

Hello list, my question is related to svd of a matrix: b=matrix(rnorm(50),10,5) mysvd=svd(b) I would like to compute each xi where xi = di* ui %*% t(vi). I do it by : xlist=sapply(1:ncol(b), function(x1,y) y$d[x1]*y$u[,x1]%*%t(y$v[,x1]),y=mysvd,simplify=F) # result is a list xarray=array(sapply(1:ncol(b), function(x1,y) y$d[x1]*y$u[,x1]%*%t(y$v[,x1]),y=mysvd),c(nrow(b),ncol(b),ncol(b))) #

Hello, i' m looking for a function to compute geary statistic for spatial correlation. Thanks. -- St?phane DRAY --------------------------------------------------------------- Biom?trie et Biologie ?volutive - Equipe "?cologie Statistique" Universite Lyon 1 - Bat 711 - 69622 Villeurbanne CEDEX - France Tel : 04 72 43 27 56 Fax : 04 78 89 27 19 04 72 43 27 57 E-mail

Dear List: Is any one aware of a package that would extend the D() function and allow for one to maximize a likelihood function symbolically? Something akin to Solve[x==0, parameter] function in Mathematica? Clearly R has the capacity to _compute_ MLEs given a set of data. But, I'm looking for a package that would allow for me to define the likelihood function, find the 1st order partial

Hello, I am trying to play with RODBC library and Excel Files. In my file (doubs.xls) there are 2 spreadsheets: > library(RODBC) > connection<-odbcConnect("Excel Files") > sqlTables(connection) TABLE_CAT TABLE_SCHEM TABLE_NAME TABLE_TYPE REMARKS 1 F:\\Th?se\\R\\Doubs NA Faune$ SYSTEM TABLE NA 2 F:\\Th?se\\R\\Doubs NA Milieu$

Hi, can anyone tell me if R can be used to rearrange very complicated equations in terms of one of the variables? I have: dx/dt = a*b*m*y*(1-x)-r*x and, having set: dy/dx = 0, need to rearrange in terms of x. The problem I have is that I don't know how to rearrange equations when the variables are not yet defined (I get messages warning me that x etc can't be found). I'm not sure

Dear all, I am trying to compile Ralpha on my computer (OS = Debian). SVN Revision is: Revision: 42843 Last Changed Date: 2007-09-14 ./configure returns : ---------------------------------------------------- stephane at pcdray:~/Rdev/R-alpha$ ./configure checking build system type... i686-pc-linux-gnulibc1 checking host system type... i686-pc-linux-gnulibc1 loading site script

Hello list, (PC Windows 2000, R 1.2.3) i want to compile C source file for R on windows 2000. I'm working with Metrowerks CodeWarrior for creating and compiling C files. I've see that R.lib file must be obtain with R.ddl by Visual C++. I don't have Visual C++ (and i don't want to buy it !!) but i want to obtain R.lib file. Is there a solution to my problem ??? Any help would

Hello, I am trying to find the analytical solution to this differential equation dR/dt = k1*R (1-(R/Rmax)^k2); R(0) = Ro k1, k2, and Rmax are parameters that need to fitted, while Ro is the baseline value (which can be fitted or fixed). The response (R) increases initially at an exponential rate governed by the rate constant k1. Response has a S-shaped curve as a function of time and it

Is there a way to find all roots of a polynomial equation? Lets say x^5+a*x^4+b*x^3+c*x^2+d*x+e=0 how to find its all roots? [[alternative HTML version deleted]]