How to fill matrix columns from array of vectors?

[Nikolay Evdokimov]

Hello, I want to fill my matrix from array of vectors by appending or assinging them.

(the code is just to show the problem)

matrix[rowsN, factorsCount] allFactors;

from some source data 

vector[rowsN] factors[factorsCount];

ways to do it could be:

for(i in 1:factorsCount)

{

       allFactors[,i] =factors[i] ;

}

or may be I should declare empty matrix and then concatenate it with vectors...

matrix[rowsN, factorsCount] allFactors;

for(i in 1:factorsCount)

{

       allFactors =append_col(allFactors, factors[i]) ;

}

Both approaches give error from the compiler:

"Not a legal assignment, sampling, or function statement.  Note that

  * Assignment statements only allow variables (with optional indexes) on the left;

    if you see an outer function logical_lt (<) with negated (-) second argument,

    it indicates an assignment statement A <- B with illegal left

    side A parsed as expression (A < (-B))."

Which is the correct way to fill matrix from array of vectors?

Regards,

Nikolay

[Nikolay Evdokimov]

oh, sorry.

 allFactors[,i] <-slowFactors[i];

seems to work fine;

just misused = and <-

[Bob Carpenter]

Can you show us a real example. For the toy example you gave, the
right approach would be to declare the variable with the shape you
want to begin with.

And it's "<-" not "=" for assignment in Stan.

- Bob

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[David Manheim]

One real example I've been hit with is when I need to re-construct a matrix inside of the ODE, since I can't pass it matrix data types :(

[Bob Carpenter]

Although that's not an array of vectors, either, we're
sympathetic to that problem. We need functions that will
start at index N in an array and peel off any given Stan
data type. We have all that in C++ as part of our I/O,
but not exposed as functions in Stan. But it's on our to-do list.

For now, you can use the new slicing functions, though it
looks like there are still some include issues that's blocking
the full functionality there.

- Bob