[Rcpp-devel] variable affectation in Rcpp Rcpp Armadillo

Well,

That's sound good,
The distribution I need are multivariate normal, inverse gaussian.
Though, the biggest issue is that for one of the parameter there is  
no closed form so I am using Metropolis Hastings for it.
Any idea about this variable reaffectation thing?
It seems to be specific to arma classes like arma::mat

Nicolas

On Wed, Jun 15, 2011 at 8:10 PM, Whit Armstrong <armstrong.whit at gmail.com 

wrote:

I'm not giving up yet.  I'll implement the distribution that is
missing, and send you the example if you lay out your model w/
pseudocode.

-Whit


On Wed, Jun 15, 2011 at 7:59 PM, Nicolas Heslot <nh269 at cornell.edu>  
wrote:

Hi,

Thank you for your quick answer.
Sorry that I did not explain well enought my issue.
I did not know about cppbugs but I just checked and it does not  

seem that I

can use it for my model because it lacks some of the distribution  

I need.

The fraction of code could seems obscure but it is just the  

updating for a

block of parameters in the model.
My problem is rather simple I think.
Once I affect a matrix to a variable I can't manage to overwrite  

the content

of that variable with a different matrix. I really can't figure  

out how to

do it.

Nicolas

On Wed, Jun 15, 2011 at 7:52 PM, Dirk Eddelbuettel  

<edd at debian.org> wrote:

Salut Nicolas,

On 15 June 2011 at 17:03, Nicolas Heslot wrote:
| Hi rcpp-devel!
| First of all thank you for this awesome tool!

Pleasure, and welcome.

| I started a few days ago coding with Rcpp to try to reduce the  

computing

time
| of a MCMC model.
| However, I don't have experience with C/C++ and I can't figure  

out how

to
| reaffect a new content to a variable.
| This seems probably very simple to you but I can't figure it  

out, and

this is
| the last step preventing my code to work out I think...
| The objects all_ui, all_ui2, all_ui3, all_rd and all_corMat are  

list

objects
| containing matrix
| But once a matrice extracted from one of those lists is  

affected, to let

say
| the object ui I can't affect the next matrix to ui at the next
iteration.
| I tried to find a way to eliminate the object at each iteration  

or to

empty it
| using .reset but without success.
|
| So any help would be very much appreciated!
| (fragment of code posted below)
|
| arma::mat tmp;
| arma::mat tmp2;
| arma::mat tmp3;
| arma::mat ui;
| arma::mat ui2;
| arma::mat ui3;
| arma::mat sigma;
|
| for (int j = 0; j < P-1; j++) {
| tmp2.fill(0);
| tmp3.fill(0);
|  for (int i = 0; i < N-1; i++) {
|  ui = all_ui[i];
| ui2 = all_ui2[i];
|  ui3 = all_ui3[i];
| rdi = all_rd[i];
| all_corMati = all_corMat[i];
|  sigma = sigma2*all_corMat[i];
| // calculate mean and variance
| arma::mat tmp = (solve(sig%all_corMat[i])* gen_a(i,j))*all_ui[i];
| arma::mat tmp2 += (all_rd[i] -
mu*trans(all_ui3[i])-(X(i)*alpha)*trans(all_ui2
| [i]) + gen_a(i,j)*a.row(j)*trans(all_ui[i]))*tmp;
| arma::mat tmp3 += (gen_a(i,j)*trans(all_ui[i]))*tmp;
| }
| }
|
| Thank you for your help

I'm with Whit here and confess that I do not know your question  

is. If you

show us what you tried, what you expected to happen and what  

actually

happened we may help.

(By the way, there is no tax on indentation in code and it does  

make it

more
readable for those of us who didn't write it ;-)

Dirk

| It probably does not help much
| but I use R2.13 with the last version of the packages on a  

windows XP

plateform
|
| Nicolas
|
|
|  

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