Dear All
I new to using R and am struggling with some matrix multiplication.
I have two matrices, one containing random numbers, these are multiplied
together to get another matrix which is different each time. When I put in
another for loop to repeat this process a multiple times the matrices are
all the same. I?m sure there is a way to keep the randomness of the
different matrices but I think I?m putting the for loop in the wrong place.
Also when I try and save the matrices using write.table only the first one
is saved
The code so far is below, any help would be greatly appreciated
Cheers
Tom
InitialPop<-matrix(c(500,0,0,0,0,0,0))
matmult<-function(InitialPop,N){
mat3<-matrix(c(0,rnorm(1,0.6021,0.0987),0,0,0,0,0,0,0,rnorm(1,0.6021,0.0987),0,0,0,0,1.9,0,0,rnorm(1,0.6021,0.0987),0,0,0,4.8,0,0,0,rnorm(1,0.6021,0.0987),0,0,9.7,0,0,0,0,rnorm(1,0.6021,0.0987),0,18,0,0,0,0,0,rnorm(1,0.6021,0.0987),32.6,0,0,0,0,0,0),nrow=7)
for (i in 1:N){
PVAmatrix<-matrix(c(0,rnorm(1,0.6021,0.0987),0,0,0,0,0,0,0,rnorm(1,0.6021,0.0987),0,0,0,0,1.9,0,0,rnorm(1,0.6021,0.0987),0,0,0,4.8,0,0,0,rnorm(1,0.6021,0.0987),0,0,9.7,0,0,0,0,rnorm(1,0.6021,0.0987),0,18,0,0,0,0,0,rnorm(1,0.6021,0.0987),32.6,0,0,0,0,0,0),nrow=7)
mat3<-mat3%*%PVAmatrix
}
ans<-mat3 %*% InitialPop
return(ans)
}
z<-matmult(InitialPop,1)
for (i in 1:4) print(z[,1])
write.table((z),"c:\\Documents and Settings\\...........................)
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I am not sure what you mean by being the same each time. If I make successive calls to the function, I get different results:> z[,1] [1,] 0.0000 [2,] 0.0000 [3,] 201.6382 [4,] 0.0000 [5,] 0.0000 [6,] 0.0000 [7,] 0.0000> matmult(InitialPop,1)[,1] [1,] 0.000 [2,] 0.000 [3,] 130.998 [4,] 0.000 [5,] 0.000 [6,] 0.000 [7,] 0.000> matmult(InitialPop,1)[,1] [1,] 0.0000 [2,] 0.0000 [3,] 219.5943 [4,] 0.0000 [5,] 0.0000 [6,] 0.0000 [7,] 0.0000> matmult(InitialPop,1)[,1] [1,] 0.0000 [2,] 0.0000 [3,] 200.0077 [4,] 0.0000 [5,] 0.0000 [6,] 0.0000 [7,] 0.0000> matmult(InitialPop,1)[,1] [1,] 0.0000 [2,] 0.0000 [3,] 256.1736 [4,] 0.0000 [5,] 0.0000 [6,] 0.0000 [7,] 0.0000 On Wed, Sep 9, 2009 at 9:36 AM, RFish<tomworthington at talk21.com> wrote:> > Dear All > > I new to using R and am struggling with some matrix multiplication. > > I have two matrices, one containing random numbers, these are multiplied > together to get another matrix which is different each time. When I put in > another for loop to repeat this process a multiple times the matrices are > all the same. I?m sure there is a way to keep the randomness of the > different matrices but I think I?m putting the for loop in the wrong place. > Also when I try and save the matrices using write.table only the first one > is saved > > The code so far is below, any help would be greatly appreciated > > Cheers > > Tom > > InitialPop<-matrix(c(500,0,0,0,0,0,0)) > > matmult<-function(InitialPop,N){ > mat3<-matrix(c(0,rnorm(1,0.6021,0.0987),0,0,0,0,0,0,0,rnorm(1,0.6021,0.0987),0,0,0,0,1.9,0,0,rnorm(1,0.6021,0.0987),0,0,0,4.8,0,0,0,rnorm(1,0.6021,0.0987),0,0,9.7,0,0,0,0,rnorm(1,0.6021,0.0987),0,18,0,0,0,0,0,rnorm(1,0.6021,0.0987),32.6,0,0,0,0,0,0),nrow=7) > > for (i in 1:N){ > PVAmatrix<-matrix(c(0,rnorm(1,0.6021,0.0987),0,0,0,0,0,0,0,rnorm(1,0.6021,0.0987),0,0,0,0,1.9,0,0,rnorm(1,0.6021,0.0987),0,0,0,4.8,0,0,0,rnorm(1,0.6021,0.0987),0,0,9.7,0,0,0,0,rnorm(1,0.6021,0.0987),0,18,0,0,0,0,0,rnorm(1,0.6021,0.0987),32.6,0,0,0,0,0,0),nrow=7) > mat3<-mat3%*%PVAmatrix > } > > ans<-mat3 %*% InitialPop > > return(ans) > > } > > z<-matmult(InitialPop,1) > for (i in 1:4) print(z[,1]) > write.table((z),"c:\\Documents and Settings\\...........................) > > -- > View this message in context: http://www.nabble.com/Matrix-multiplication-and-random-numbers-tp25365184p25365184.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. >-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve?
RFish wrote:> > I new to using R and am struggling with some matrix multiplication. >I'm not sure what you're trying to print, but you could place this vector in an expression mat3<-expression(c(0,rnorm(1,0.6021,0.0987),0,0,0,0,0,0,0,rnorm(1,0.6021,0.0987),0,0,0,0,1.9,0,0,rnorm(1,0.6021,0.0987),0,0,0,4.8,0,0,0,rnorm(1,0.6021,0.0987),0,0,9.7,0,0,0,0,rnorm(1,0.6021,0.0987),0,18,0,0,0,0,0,rnorm(1,0.6021,0.0987),32.6,0,0,0,0,0,0)) # and then evaluate to get a new matrix each time matrix(eval(mat3), nrow=7) #I think this may be easier to follow. First create a matrix of zeros, stick in fertilities and then add random survival probabilities each time mat3<-diag(0,7) #fertilities mat3[1,3:7]<-c(1.9, 4.8, 9.7, 18, 32.6) # random survival on sub-diagonal mat3[row(mat3)==col(mat3)+1]<-rnorm(6,0.6021,0.0987) # and if you want to project the population over 10 time steps in a loop ? n<-matrix(c(500,0,0,0,0,0,0)) popsize <- matrix(numeric(7 * 10), nrow = 7) for (i in 1:10) { popsize[, i] <- n mat3[row(mat3)==col(mat3)+1]<-rnorm(6,0.6021,0.0987) n <- mat3 %*% n } [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [1,] 500 0.0000 0.0000 531.6256 709.89940 940.19337 1697.52862 3403.6610 [2,] 0 352.5116 0.0000 0.0000 298.97874 424.71160 561.32525 1027.1605 [3,] 0 0.0000 279.8029 0.0000 0.00000 231.45988 316.83352 424.8883 [4,] 0 0.0000 0.0000 147.8957 0.00000 0.00000 136.36804 220.7370 [5,] 0 0.0000 0.0000 0.0000 96.92715 0.00000 0.00000 108.6551 [6,] 0 0.0000 0.0000 0.0000 0.00000 69.87527 0.00000 0.0000 [7,] 0 0.0000 0.0000 0.0000 0.00000 0.00000 65.86229 0.0000 Chris Stubben -- View this message in context: http://www.nabble.com/Matrix-multiplication-and-random-numbers-tp25365184p25369495.html Sent from the R help mailing list archive at Nabble.com.