How change (update) info items?

💬 Support & Discussions
1
  • MNE version: e.g. 0.24.0
  • operating system: Windows 10

Dear Sr,

I dont want to create a new raw.info. I want to update some info from file without destroying the rest.

Problem: mne.Info quote:
" This class should not be instantiated directly. To create a measurement information structure, use mne.create_info()."

can’t I just:

raw.info[‘description’] = ‘My custom dataset’
?

Besides
how to update multiple fields in subject_info:

Last name.
First name.
Middle name.
Birthday in (year, month, day) format.
Subject sex (0=unknown, 1=male, 2=female).
Handedness (1=right, 2=left, 3=ambidextrous).

Is it something like
raw.create_info(“Last name” = Kanda)
?

One last question: how long can be the text in cases as →
Pages.EEG_raw.info[‘description’] = “a small string the size of a book…”

Could you show me a code example. I couldn’t find any.

Thanks in advance.

Paulo Kanda

2

Did you read the rest of the mne.Info docstring? It says, among other things:

The only entries that should be manually changed by the user are info['bads'], info['description'], info['device_info'], info['dev_head_t'], info['experimenter'], info['helium_info'], info['line_freq'], info['temp'] and info['subject_info']. All other entries should be considered read-only, though they can be modified by various MNE-Python functions or methods (which have safeguards to ensure all fields remain in sync).

So you can certainly do things like raw.info['description'] = 'whatever'. I don’t know if the length of the string is limited; we don’t limit it in our code but it might be constrained by the .fif file format when saving the info, or when saving a data object with that info attached to it. @larsoner probably knows that answer.

subject_info is also in the above list of entries that may be changed by the user. So raw.info['subject_info'] = some_dict is fine, as is raw.info['subject_info'].update(last_name='Kanda', first_name='Paolo', ...)

3

To further clarify: what this means

is that you should not do my_new_info = mne.Info(...) (that would be “direct class instantiation”) but instead you should do my_new_info = mne.create_info(...) (using our function to create an instance of the Info class). The function is preferred because it has lots of built-in safety checks to make sure your Info object is consistent / has everything it needs to work properly with our data classes like Raw, Epochs, etc. But both of these possibilities apply when you want a new Info object, not when you want to update fields in an existing Info object. For that, see my prior answer above.

4

AFAIK there isn’t any real limit on the str size. I think in practice you’re going to hit problems as you get close to 2GB, but hopefully your info['description'] doesn’t get close to this :slight_smile:

5

Did you read the rest of the mne.Info docstring? It says, among other things…

Yes, I read that. My doubt was about having to update all the dic.

All that info was enlightening!!

Thank you again.

6

Just in case it can help anyone else:

    Pages.EEG_raw.info['subject_info'] = {"last_name":"Kanda",
                                          "first_name":"Paolo",
                                          "middle_name":"Medeiros",
                                           "birthday":(1971,9,10),
                                           "sex":1,
                                           "hand":1}
    print(Pages.EEG_raw.info['subject_info'])

{‘last_name’: ‘Kanda’, ‘first_name’: ‘Paolo’, ‘middle_name’: ‘Medeiros’, ‘birthday’: (1971, 9, 10), ‘sex’: 1, ‘hand’: 1}

and to get info back:

    print(Pages.EEG_raw.info['subject_info']['last_name'])

kanda