Custom meta field checkbox

I’m trying to create a meta box checkbox but I can’t get it to work.. I’m using the function reference at https://codex.www.ads-software.com/Function_Reference/add_meta_box

The code I’m using for the check-box meta is,

echo '<label for="myplugin_new_field">' . __("Description for this field", 'myplugin_textdomain' ) . '</label> ';
  echo '<input type="checkbox" name="myplugin_new_field" id="myplugin_new_field" value="yes"';
                                    if ( get_post_meta('myplugin_new_field', true ) == "yes" )
                                        echo ' checked="checked"';
                                    echo '" style="width: auto;" />';
}

The checkbox appears in edit post pages without any errors. I check it but after I update the post it becomes unchecked.
Not sure what I’m doing wrong here..