On executing sudo-apt get update it gives me the following:  Err:4 https://deb.torproject.org/torproject.org bionic InRelease                              The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 74A941BA219EC810 Err:7 http://in.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages                   Hash Sum mismatch   Hashes of expected file:    - Filesize:563484 [weak]    - SHA256:922599efa85df1c8960535da907026555b19006ab321005918b75de76cae422b    - SHA1:19064dc18593afe6046b03a6506e0a01784ce544 [weak]    - MD5Sum:4dd7ac9ab795941bc74b13ec681f17c2 [weak]   Hashes of received file:    - SHA256:fd3c8f7b50c7f36970d1afd8233694a07cab0fb387de60ff185d7743757db679    - SHA1:18b139b4eb060ba013cac731aa0d4c6e0f5113c9 [weak]    - MD5Sum:acf7d58d48ce5177419214c8196b9745 [weak]    - Filesize:563484 [weak]   Last modification reported: Sun, 28 Jul 2019 01:57:06 +0000   Release file created at: Mon, 29 Jul 2019 07:43:31 +0000 Reading package lists... Done                                    W: GPG error: https://deb.torproject.org/torproject.org bionic InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 74A941BA219EC810 E: The repository 'https://deb.torproject.org/torproject.org bionic InRelease' is not signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.   After this error, somebody suggested me to execute the following  : sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 74A941BA219EC810  And this is what is output on the terminal:  Executing: /tmp/apt-key-gpghome.serEMDJCIi/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 74A941BA219EC810 gpg: packet(13) too large gpg: read_block: read error: Invalid packet gpg: no valid OpenPGP data found. gpg: Total number processed: 0   Kindly help!
I added some extra repositories with the Software Sources program. But when I reload the package database, I get an error like the following:     W: GPG error:  trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8BAF9A6F   I know I can fix it using apt-key in a terminal, according to the official Ubuntu documentation. But I would have liked to do it graphically. Is there a way to do this without using a terminal?
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In that paper, the authors explain that features are indicator functions that take into account certain aspects of the text. The problem is that this aspects affect the maximum entropy function.  In the case of parsing, I have problems understanding the concept of features. For parsing one must have:   Two sets, $X$ for the sentences and $Y$ for the parses For each sentence $x \in X$, one must have the N-best list of candidate parses; denoted $GEN(x) \subset Y$. Training samples $(x_j,y_j)$. The $x_j$ are sentences and the $y_j$ are parses. And a feature mapping $\Phi(X,Y)$ that maps each pair (x,y) to a vector of feature values.   The problem of parsing will consist of finding the weight vector such that the following expression is minimized  $$ -\sum log P(y_j|x_j,w) + \lambda ||w||_1 $$  where   $$ P(y_j|x_j,w) = \frac{exp \{w^T \Phi(x_j,y_j)\}   }{ \sum_{u \in GEN(x)} exp\{ w^T\Phi(x_j,u) \}  } $$  My question is, what are the features in this case? 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