# Error in combining edf files
**URL:** https://mne.discourse.group/t/error-in-combining-edf-files/1380
**Category:** Mailing List Archive (read-only)
**Tags:** list-archive
**Created:** [December 4, 2017, 1:51am UTC](https://mne.discourse.group/t/error-in-combining-edf-files/1380 "2017-12-04T01:51:36Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@system](https://mne.discourse.group/u/system)
#### Post date: [December 4, 2017, 1:51am UTC](https://mne.discourse.group/t/error-in-combining-edf-files/1380/1 "2017-12-04T01:51:36Z")
Hi,
I am trying to combine two edf files with the following code,
raw0 = mne.io.read\_raw\_edf('file1', preload=True)
raw1 = mne.io.read\_raw\_edf('file2', preload=True)
raw = raw0.append(raw1)
When I try to plot 19th channel with the following code,
data = raw[:, :][0]
plt.plot(data[19])
plt.show()
Following set of error comes
TypeError Traceback (most recent call
last)\ in \()----\> 1 data =
raw[:, :][0] 2 plt.plot(data[19]) 3 plt.show()
TypeError: 'NoneType' object is not subscriptable
What is wrong with my code?
?
\<[https://mailtrack.io/](https://mailtrack.io/)\> Sent with Mailtrack
\<[https://chrome.google.com/webstore/detail/mailtrack-for-gmail-inbox/ndnaehgpjlnokgebbaldlmgkapkpjkkb?utm\_source=gmail&utm\_medium=signature&utm\_campaign=signaturevirality](https://chrome.google.com/webstore/detail/mailtrack-for-gmail-inbox/ndnaehgpjlnokgebbaldlmgkapkpjkkb?utm_source=gmail&utm_medium=signature&utm_campaign=signaturevirality)\>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: [http://mail.nmr.mgh.harvard.edu/pipermail/mne\_analysis/attachments/20171204/5d816697/attachment.html](http://mail.nmr.mgh.harvard.edu/pipermail/mne_analysis/attachments/20171204/5d816697/attachment.html)
---
### Author:  [@system](https://mne.discourse.group/u/system)
#### Post date: [December 4, 2017, 2:39am UTC](https://mne.discourse.group/t/error-in-combining-edf-files/1380/2 "2017-12-04T02:39:32Z")
Hi Senaka,
The append method is an in-place operation so when you assign it to raw,
there is no returned value and therefore it is then mapped to None.
To remedy it, just try `raw0.append(raw1)` and proceed with raw0 for
following steps.
HTH,