[FIX] unicode: replace greek mu and omega by micro and ohm signs

[sappelhoff]

There is actually a difference between µ and μ.

Previously we had the greek Mu sign, but what we really want is the micro sign.

cf. https://twitter.com/stefanappelhoff/status/1055122338080006144

edit: This same error was also true for the omega sign, which should be an ohm sign:

• https://www.compart.com/en/unicode/U+03A9
• https://www.compart.com/en/unicode/U+2126

[jasmainak]

This should not happen though. See quote from wikipedia below:

The symbol for the prefix comes from the Greek letter μ (mu)

probably something to do with UTF8 vs ASCII ?

[sappelhoff]

The symbols have different unicode signs (U+00B5 vs. U+03BC), so copy pasting from the spec (as I did) can lead to problems.

In my case this was indeed a UTF-8 / ASCII issue (Python3 vs. Python2)

[jasmainak]

ah I see. Seems nasty. Perhaps something to check in the validator too?

[chrisgorgo]

@jasmainak perhaps, but would not make it a high priority (worth opening an issue anyway).

Pinging @bids-standard/bep_leads for comments. Unless anyone objects I will merge this on 2018-11-02.

[sappelhoff]

Perhaps something to check in the validator too?

+1

... as far as I know there are no unit checks implemented anyways at this point. So this adds one to the list.

[dorahermes]

we had a long discussion about these units (which I can't find, maybe @robertoostenveld @choldgraf ?), but I remember a useful suggestion from @satra about the symbol used for micro

[satra]

here is the ascii-based units representation we discussed:

http://people.csail.mit.edu/jaffer/MIXF/MIXF-10

[jasmainak]

ascii-based unit representations sound like a great idea!

[chrisgorgo]

Is the consensus to go with @satra suggestion instead of this PR? If so @sappelhoff could you update your branch accordingly?

[sappelhoff]

Sure, but does accepting the ascii-based units mean rejecting the other units?

I could imagine leaving our units as they are currently (plus the fix of this PR) ... and then adding a link to our document that links to the ascii units suggested by @satra

[CPernet]

I'm happy with ACII, in Matlab I coded in eeglab for char(181) that's micro (even if matlab says mu, char(956) is mu)

…

-- Dr Cyril Pernet, Senior Academic Fellow Neuroimaging Sciences Centre for Clinical Brain Sciences Chancellor's Building, Room GU426D The University of Edinburgh 49 Little France Crescent Edinburgh BioQuarter EH16 4SB cyril.pernet@ed.ac.uk tel: +44 (0)131 465 9530 http://www.sbirc.ed.ac.uk/cyril http://www.ed.ac.uk/edinburgh-imaging <http://www.ed.ac.uk/edinburgh-imaging>

________________________________ From: Stefan Appelhoff <notifications@github.com> Sent: 08 November 2018 21:41 To: bids-standard/bids-specification Cc: PERNET Cyril; Team mention Subject: Re: [bids-standard/bids-specification] [minor] replace greek mu by micro sign (#73) Sure, but does accepting the ascii-based units mean rejecting the other units? I could imagine leaving our units as they are currently (plus the fix of this PR) ... and then adding a link to our document that links to the ascii units suggested by @satra<https://github.com/satra> — You are receiving this because you are on a team that was mentioned. Reply to this email directly, view it on GitHub<#73 (comment)>, or mute the thread<https://github.com/notifications/unsubscribe-auth/AEjUDjAdJ6BNIt2UbmiajJV0T6qXF_TGks5utKUYgaJpZM4X9TpL>. The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336.

[sappelhoff]

@chrisfilo: in my opinion, this PR should be merged and we should have a separate discussion whether or not we want ...

• ...the existing unicode representation for unit symbols and prefixes
• ...a pure ASCII representation
• ...a mixture of both