I was writing a Stan program and some issues came up: Linear interpolation. I wanted to create a function that interpolates, something like this: vector[N] x0; vector[N] y0; The function f(y) interpolates: If x < x0[1], then y = x0[1]; If x is between x0[n] and x0[n+1], then y interpolates b…

Maybe we can make a variadic version of this? stan-dev/math/blob/develop/stan/math/prim/mat/fun/append_array.hpp #ifndef STAN_MATH_PRIM_MAT_FUN_APPEND_ARRAY_HPP #define STAN_MATH_PRIM_MAT_FUN_APPEND_ARRAY_HPP #include <stan/math/prim/meta.hpp> #include <stan/math/prim/mat/fun/Eigen.hpp> #i…

The lack of a variadic version of vector concatenation has come up very recently, although the interest there was for use in the generated quantities. [image] Append multiple vectors with append_row in generated quantities Modeling I have what I assume to be a simple ques…

This one is really simple actually. For the simpler case with vectors of the same type I threw together a prototype that reduces the copies and a simple test . In terms of the math library this can be done pretty easy. The tougher problems is how do you specify a variadic function in function signat…

It would be great to have concatenation. The big thing, though, would be if we could treat vectors and 1-D real arrays as equivalent, and treat matrices and 2-D real arrays as equivalent. I spend lots and lots of time when coding, going back and forth between real theta[N]; and vector[N] theta;. S…

So basically we should make overloads of all (or majority) functions that you can do on vectors to also support real arrays and vice-versa? I suspect the efforts of @stevebronder to make functions more general should help us a lot here. Can you list a few that dont work on both?

Within some limits you can code up something with Stan already now which does nice concatenation: // takes as input an array of the form {a,b,c,d} where a,b,c,d are // real 1d arrays. These are then returned as concatenated 1d array real[] concatenate_real_array(real[,] elems); real[] concatenate_r…

Wasn’t the plan for Stan 3 to remove the distiction between reals and vectors? I thought I read something like that perhaps on the wiki.

Mcol: That would be great, to remove the distinction between reals and vectors. Would we also remove the distinction between 2-d arrays and matrices?

Hi, here’s a very simple example of why this improvement will make a big difference in the real world. First version of model: data { int<lower=0> J; real y[J]; real<lower=0> sigma[J]; } parameters { real mu; real<lower=0> tau; real eta[J]; } model { eta ~ normal(0, 1); y ~ normal(mu +…

[image] wds15: Within some limits you can code up something with Stan already now which does nice concatenation Can a, b, c, d be of different length? Because real[,] is a square structure.

Vectors/arrays, interpolation, other things

Modeling

mcol August 15, 2019, 6:02pm 3

The lack of a variadic version of vector concatenation has come up very recently, although the interest there was for use in the generated quantities.

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Concatenating N vectors General	21	1351	July 21, 2021
Declaring a Vector and adding elements in it General	13	2719	April 23, 2020
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Vectors/arrays, interpolation, other things

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