Quick question, can I assign a vector as a single element in an array of reals?

#1

For bringing a vector into the integrate_ode function, could I assign the vector as a single element in an array of reals x_r? For example,

data {
    vector[5] test_vector;
}

transformed data {
    real x_r[10];
    x_r[1] = test_vector;
}

Is that a possible operation? If not, the plan was to use the to_array_1d function to convert the vector into an array of reals.

#2

No, sorry, right now you’ve got to manually pack and unpack everything from 1d arrays. It’s awkward.

We’re working on something right now to address this problem (https://github.com/stan-dev/math/pull/1641) but that won’t be finished until later this year (knock on wood).

#3

Hi @bbbales2, thanks for your help again. So, I take it that it would also be impossible to assign an array of reals to a single element in x_r? Best way then would be to write a for loop that assigns individual elements from test_vector to x_r per iteration?

#4

Only way, unfortunately.

#5

Roger that, thank you!

#6

The to_array_1d function will work, although it only saves you a few keystrokes.

rstan::lookup("to_array_1d")
#7

Sorry, @bgoodri, for clarification, you’re saying assigning an array of reals to an individual element of x_r will work?

#8

I just meant coercing a vector to a one-dimensional array of reals works. It will still be unpacked.