# Why does stc.save() save two .stc files? **URL:** \ **Category:** Mailing List Archive (read-only)\ **Tags:** list-archive\ **Created:** [August 29, 2017, 2:57pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292 "2017-08-29T14:57:15Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [August 29, 2017, 2:57pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/1 "2017-08-29T14:57:15Z")
Hi, I'm wondering why saving a source estimate using stc.save(fname,...) saves both lh.stc and rh.stc files when each of these already contains both hemispheres' data. Is there a difference between the lh.stc and rh.stc files? Thanks and Best, Gladia -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170829/9746f0a2/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170829/9746f0a2/attachment.html) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [August 29, 2017, 4:09pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/2 "2017-08-29T16:09:41Z")
lh.stc only contains values for left hemisphere and vice verse. So it's not redundant. HTH Alex -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170829/e53be01a/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170829/e53be01a/attachment.html) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [August 29, 2017, 5:33pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/3 "2017-08-29T17:33:12Z")
Hi Alex, When I read in either an lh.stc or an rh.stc file using mne.read\_source\_estimates, the stc object contains both stc.lh\_data and stc.rh\_data. Also, the stc object contains vertex lists for both hemispheres (lh\_vertno and rh\_vertno). Should I only use stc.lh\_data from the lh.stc file and stc.rh\_data from the rh.stc file? Thanks and Best, Gladia ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [August 29, 2017, 7:59pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/4 "2017-08-29T19:59:42Z")
yes use lh\_data and rh\_data to select data from lh or rh FYI we use internally this private function to read each file: [https://github.com/mne-tools/mne-python/blob/master/mne/source\_estimate.py#L34](https://github.com/mne-tools/mne-python/blob/master/mne/source_estimate.py#L34) HTH Alex -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170829/c894eef7/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170829/c894eef7/attachment.html) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [September 6, 2017, 1:26pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/5 "2017-09-06T13:26:09Z")
Hi Alex, Sorry to ask again, but I still can't figure it out. Each time I do stc.save(), two files are saved: \-lh.stc and \-rh.stc. The lh.stc file contains both lh\_data and rh\_data. The rh.stc file also contains both lh\_data and rh\_data. I have verified that lh\_data from the lh.stc file is identical to lh\_data from the rh.stc file. Similarly, rh\_data from the lh.stc file is identical to rh\_data from the rh.stc file. Therefore I am unsure why two files were created by the stc.save() function. Because I am morphing the data in the stc files, it would cut the computation time in half if I could morph only one set of files (eg. just the lh.stc files, which already contain both hemispheres' data). I'd like to make sure that it's ok to morph just one set of stc files (lh.stc)- that there's no extra information stored in the other set (rh.stc files). Thanks and Best, Gladia ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [September 6, 2017, 1:33pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/6 "2017-09-06T13:33:15Z")
> Each time I do stc.save(), two files are saved: \-lh.stc and > \-rh.stc. Yep, this is correct. > The lh.stc file contains both lh\_data and rh\_data. The -lh.stc file on disk only contains the left-hemisphere data. But in MNE if you tell it to load the -lh.stc file, it automatically loads both the -lh.stc \*and\* -rh.stc files to give you the SourceEstimate. Eric -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170906/70351d72/attachment-0001.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170906/70351d72/attachment-0001.html) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [September 6, 2017, 2:05pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/7 "2017-09-06T14:05:56Z")
how come you can have the same values in lh\_data and rh\_data? can you share the files? Alex -------------- next part -------------- An HTML attachment was scrubbed... URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20170906/ae3356b6/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20170906/ae3356b6/attachment.html) ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\ **Post date:** [September 6, 2017, 3:50pm UTC](https://mne.discourse.group/t/why-does-stc-save-save-two-stc-files/1292/8 "2017-09-06T15:50:37Z")
Hi Eric, I see, thank you! Hi Alex, I don't have the same values in rh\_data and lh\_data. I have two copies of lh\_data and rh\_data, one loaded from the lh.stc file and the other from the rh.stc file. However, Eric's explanation clarifies why I still need both lh.stc and rh.stc files. Best, Gladia