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## Re: error "can't perform indexing operations for <unknown type> type"

**From**: |
David Bateman |

**Subject**: |
Re: error "can't perform indexing operations for <unknown type> type" |

**Date**: |
Sat, 15 Oct 2005 21:32:24 +0200 |

**User-agent**: |
Mozilla Thunderbird 1.0.2 (Windows/20050317) |

cmire a écrit :

`I'm new to Octave, and I've got a short Matlab program from a professor that
``we are supposed to modify to solve some homework problems. I've read that
``Octave can run Matlab code (I've updated the ~/octaverc file accordingly,
``etc.).
`

`When I try to run the code using the command "source(Exercise.m)", I get the
``output:
`
length = 10
npoints = 200
mass = 0.070000
num_sol = 4
error: can't perform indexing operations for <unknown type> type
error: evaluating argument list element number 1

`I don't need help with the actual homework assignment -- I just need to get
``this code working so I can proceed to do my homework. Help is greatly
``appreciated!
`

`
``
`

`Not sure why there is this error, and is certainly a bug in the version
``of octave you are using as it indicates that an uninitalized value is
``being returned from a compiled function, might be due to issues with eigs..
`

`In any case the only version of eigs that exists for octave is the one I
``have that has serious stability problems and only works (and then just)
``for real symmetric marices. So I haven't made this version of eigs
``available. You therefore have two choices. 1) Forget trying to use
``octave for this code, or
`2) change the eigs call to read something like
[phi,te] = eig(Hmatrix);
[te, idx] = sort(Hmatrix);
te = te(1:num_sol);
phi = phi(:,idx(1:num_sol));

`though for large matrices and small num_sol this will be significantly
``slower than using eigs as all of he eigenvectors are calculated and you
``only pick num_sol of them.
`
D.
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