[Neuroimaging] failure using DIPY Free Water Elimination DTI

[Ariel Rokem]

Hi Ping,

Thanks for your email. Hard to say exactly what is going on without further
information. Could you tell us more about the data you are using? How many
b-values? How many directions? Any chance you could share the data from the
voxel that caused that error to be raised?

Thanks!

Ariel

On Thu, Dec 27, 2018 at 6:55 AM Ping-Hong Yeh <pinghongyeh at gmail.com> wrote:

> Hi Dipy Users,
>
>  I've ran into errors "Eigenvalues did not  converge" when using the free
> water elimination model,
> and here is the error message:
>
>   File
> "/Users/yehp/anaconda3/lib/python3.6/site-packages/dipy/reconst/dti.py",
> line 1615, in _decompose_tensor_nan
>     min_diffusivity=min_diffusivity)
>   File
> "/Users/yehp/anaconda3/lib/python3.6/site-packages/dipy/reconst/dti.py",
> line 1946, in decompose_tensor
>     eigenvals, eigenvecs = eigh(tensor)
>   File
> "/Users/yehp/anaconda3/lib/python3.6/site-packages/dipy/utils/arrfuncs.py",
> line 128, in eigh
>     return np.linalg.eigh(a, UPLO)
>   File
> "/Users/yehp/anaconda3/lib/python3.6/site-packages/numpy/linalg/linalg.py",
> line 1291, in eigh
>     w, vt = gufunc(a, signature=signature, extobj=extobj)
>   File
> "/Users/yehp/anaconda3/lib/python3.6/site-packages/numpy/linalg/linalg.py",
> line 95, in _raise_linalgerror_eigenvalues_nonconvergence
>     raise LinAlgError("Eigenvalues did not converge")
> numpy.linalg.linalg.LinAlgError: Eigenvalues did not converge
>
>
> Any suggestions?
>
> Thank you.
>
> Ping
>
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