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[Octave-bug-tracker] [bug #35157] Naive users baffled by "complex scalar

From: Clem
Subject: [Octave-bug-tracker] [bug #35157] Naive users baffled by "complex scalar type invalid as index value"
Date: Fri, 23 Dec 2011 07:38:12 +0000
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0.1) Gecko/20100101 Firefox/8.0.1

Follow-up Comment #3, bug #35157 (project octave):

Hi Jordi-

I think the size and composition of Octave's user base has shifted a bit, now
that Prof Ng is using it to teach his very popular Stanford Machine Learning
course last semester and next semester.  Prof Koller will be teaching another
free Stanford course (pgm-class.org) next semester that uses Octave.  *Anyone*
in the world can sign up for these free classes.  Tens of thousands have!

I followed the class forums quite a bit.  I saw that a number of people had a
lot of catching up to do: a few people asking "what is e?"  There was at least
one enterprising High School student in the mix.  So, there's plenty of
opportunity for confusion now that the flood gates are open.

So, for better or worse, Octave is getting a big boost in popularity and some
of those users need more help than Octave users in the past.  Some users are
actually reasonably knowledgeable, but are unused to vectorization and their
Linear Algebra is very rusty or even non-existent.

Heck, I'll even confess that I was momentarily confused by this error message,
but I figured it out after a moment or two since complex numbers were not
foremost on my mind.  I wouldn't have felt insulted by my proposed error
message, although I did feel a little silly making the mistake in the first

I would agree with a premise that Octave shouldn't be "dumbed down" to help
those who probably shouldn't be using it in the first place, but a lot of
people will be using it for the first time.  IMHO, a little extra help that
doesn't get in the way of the experienced user would be ideal.

Here are a few instances of people specifically getting confused by this error
message.  For some of these people, English isn't their first language, so the
capitalization would be helpful.  I hope this helps convince you of the need.

Omar posted this:


using y alone is not working 101 not comfort with 50001

also using y(i) complex scalar type

also using(y==i)(i) complex scalar type

what should i do ?!

And Simone appears to be confused here:

Hi everyone, I keep getting this error when running recoverdata.m : error:
complex scalar type invalid as index value

And Ari was confused here:


But unfortunately it's giving me the error: complex scalar type invalid as
index value

Can anybody please tell me where I'm making the mistake. 

And Pol is puzzled in this post:


despite it is accepted by the course my error now (when finishing the 50th
iteration of the first label) is the following:

Iteration 50 | Cost: 1.359936e-02 error: complex scalar type invalid as index
value error: 


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