# Multivariate Output External Function Class

From the Examples Gallery, Using a “black box” likelihood function (numpy) — PyMC example gallery

I have attempted to modify the code to output a vector of values.

``````# define a pytensor Op for our likelihood function
class LogLike(pt.Op):

"""
Specify what type of object will be passed and returned to the Op when it is
called. In our case we will be passing it a vector of values (the parameters
that define our model) and returning a single "scalar" value (the
log-likelihood)
"""

itypes = [pt.dvector]  # expects a vector of parameter values when called
otypes = [pt.dscalar]  # outputs a single scalar value (the log likelihood)

def __init__(self, loglike, data, x, sigma):
"""
Initialise the Op with various things that our log-likelihood function
requires. Below are the things that are needed in this particular
example.

Parameters
----------
loglike:
The log-likelihood (or whatever) function we've defined
data:
The "observed" data that our log-likelihood function takes in
x:
The dependent variable (aka 'x') that our model requires
sigma:
The noise standard deviation that our function requires.
"""

# add inputs as class attributes
self.likelihood = loglike
self.data = data
self.x = x
self.sigma = sigma

def perform(self, node, inputs, outputs):
# the method that is used when calling the Op
(theta,) = inputs  # this will contain my variables

# call the log-likelihood function
logl = self.likelihood(theta, self.x, self.data, self.sigma)

outputs[0][0] = np.array(logl)  # output the log-likelihood
``````

My question is how do I modify this to output a vector. I made the change of

``````otypes = [pt.dvector]  # outputs a single scalar value (the log likelihood)
``````

but I was wondering on how to change for the size of vector I am interested in.

``````outputs[0][0] = np.array(logl)  # output the log-likelihood
``````