Hi Ricardo,

It took me some time to correctly implement pymc5 to make CustomDist work. However, once implemented, the script does not work. I don’t make it to understand the output message . Here the info. Thank you very much! (Maybe there is another option simpler than CustomDist?)

Best, Ezequiel.

```
def diag_mv_exponential_dist(lambda1, lambda2, size):
if size is None:
size = ()
return pm.Exponential.dist([lambda1, lambda2], shape=tuple(size) + (2,))
def diag_mv_exponential_logp(value, lambda1, lambda2):
# Contract logp of the pairs
return pm.logp(pm.Exponential.dist([lambda1, lambda2]), value).sum(-1)
with pm.Model() as m:
w = pm.Dirichlet('w', a=np.array([1, 1]))
mu0 = pm.Normal("mu0", mu=120, sigma=15)
mu1 = pm.Normal("mu1", mu=124, sigma=2)
sigma0 = pm.HalfNormal("sigma0", sigma=15)
sigma1 = pm.HalfNormal("sigma1", sigma=1)
lambda0 = pm.Normal("lambda0", mu=0.05, sigma=0.02)
lambda1 = pm.Normal("lambda1", mu=0.5, sigma=0.2)
diag_mv_exponential = pm.CustomDist.dist(lambda0, lambda1, dist=diag_mv_exponential_dist, logp=diag_mv_exponential_logp, ndim_supp=1, class_name="diag_mv_exponential")
diag_mv_normal = pm.MvNormal.dist(mu=[mu0,mu1], cov=[[sigma0,0],[0,sigma1]])
mymixture = [diag_mv_normal, diag_mv_exponential]
Y_obs = pm.Mixture("Y_obs", w = w, comp_dists=mymixture, observed=data)
```

And sends me the following message, which starts with a " UserWarning: CustomDist with dist function is still experimental. Expect bugs!"

```
/home/sequi/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/distribution.py:623: UserWarning: CustomDist with dist function is still experimental. Expect bugs!
warnings.warn(
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/pytensorf.py:436, in floatX(X)
435 try:
--> 436 return X.astype(pytensor.config.floatX)
437 except AttributeError:
438 # Scalar passed
AttributeError: 'list' object has no attribute 'astype'
During handling of the above exception, another exception occurred:
TypeError Traceback (most recent call last)
TypeError: float() argument must be a string or a real number, not 'TensorVariable'
The above exception was the direct cause of the following exception:
ValueError Traceback (most recent call last)
Cell In[50], line 19
16 lambda0 = pm.Normal("lambda0", mu=0.05, sigma=0.02)
17 lambda1 = pm.Normal("lambda1", mu=0.5, sigma=0.2)
---> 19 diag_mv_exponential = pm.CustomDist.dist(lambda0, lambda1, dist=diag_mv_exponential_dist, logp=diag_mv_exponential_logp, ndim_supp=1, class_name="diag_mv_exponential")
20 diag_mv_normal = pm.MvNormal.dist(mu=[mu0,mu1], cov=[[sigma0,0],[0,sigma1]])
21 mymixture = [diag_mv_normal, diag_mv_exponential]
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/distribution.py:1023, in CustomDist.dist(cls, class_name, dist, random, logp, logcdf, moment, ndim_supp, ndims_params, dtype, *dist_params, **kwargs)
1021 cls.check_valid_dist_random(dist, random, dist_params)
1022 if dist is not None:
-> 1023 return _CustomSymbolicDist.dist(
1024 *dist_params,
1025 class_name=class_name,
1026 dist=dist,
1027 logp=logp,
1028 logcdf=logcdf,
1029 moment=moment,
1030 ndim_supp=ndim_supp,
1031 **kwargs,
1032 )
1033 else:
1034 return _CustomDist.dist(
1035 *dist_params,
1036 class_name=class_name,
(...)
1044 **kwargs,
1045 )
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/distribution.py:641, in _CustomSymbolicDist.dist(cls, class_name, dist, logp, logcdf, moment, ndim_supp, dtype, *dist_params, **kwargs)
633 if moment is None:
634 moment = functools.partial(
635 default_moment,
636 rv_name=class_name,
637 has_fallback=True,
638 ndim_supp=ndim_supp,
639 )
--> 641 return super().dist(
642 dist_params,
643 class_name=class_name,
644 logp=logp,
645 logcdf=logcdf,
646 dist=dist,
647 moment=moment,
648 ndim_supp=ndim_supp,
649 **kwargs,
650 )
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/distribution.py:387, in Distribution.dist(cls, dist_params, shape, **kwargs)
385 ndim_supp = getattr(cls.rv_op, "ndim_supp", None)
386 if ndim_supp is None:
--> 387 ndim_supp = cls.rv_op(*dist_params, **kwargs).owner.op.ndim_supp
388 create_size = find_size(shape=shape, size=size, ndim_supp=ndim_supp)
389 rv_out = cls.rv_op(*dist_params, size=create_size, **kwargs)
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/distribution.py:670, in _CustomSymbolicDist.rv_op(cls, class_name, dist, logp, logcdf, moment, size, ndim_supp, *dist_params)
666 dummy_dist_params = [dist_param.type() for dist_param in dist_params]
667 with BlockModelAccess(
668 error_msg_on_access="Model variables cannot be created in the dist function. Use the `.dist` API"
669 ):
--> 670 dummy_rv = dist(*dummy_dist_params, dummy_size_param)
671 dummy_params = [dummy_size_param] + dummy_dist_params
672 dummy_updates_dict = collect_default_updates(dummy_params, (dummy_rv,))
Cell In[50], line 4, in diag_mv_exponential_dist(lambda1, lambda2, size)
2 if size is None:
3 size = ()
----> 4 return pm.Exponential.dist([lambda1, lambda2], shape=tuple(size) + (2,))
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/distributions/continuous.py:1314, in Exponential.dist(cls, lam, *args, **kwargs)
1312 @classmethod
1313 def dist(cls, lam, *args, **kwargs):
-> 1314 lam = at.as_tensor_variable(floatX(lam))
1316 # PyTensor exponential op is parametrized in terms of mu (1/lam)
1317 return super().dist([at.reciprocal(lam)], **kwargs)
File ~/miniconda3/envs/pymc_env/lib/python3.11/site-packages/pymc/pytensorf.py:439, in floatX(X)
436 return X.astype(pytensor.config.floatX)
437 except AttributeError:
438 # Scalar passed
--> 439 return np.asarray(X, dtype=pytensor.config.floatX)
ValueError: setting an array element with a sequence.
```