Hi Francesco,
I apologize for using "for" earlier, as I did not explain how you should be
using it. The comment of "do something with rel" should have indicated that
it resolved to an expression, and those expressions would be returned in a
seq (the "for" expression resolves to have a value of a seq).
Given your last example, I could read it a couple of ways. My first
interpretation is that you just need a way to convert names to nodes, and
then to connect all the nodes. My preference would be to separate these
steps, so the conversion would be done with:
(map convert-to-node list-of-names)
The result of this is then looped through to create the relations (as in my
previous example, the relations are both ways, and not reflexive):
(let [nodes (map convert-to-node list-of-names)]
(for [node1 nodes, node2 nodes :when (not= node1 node2)]
(nrl/create conn page1 page2 :links)))
This creates a seq of all the relations, in both directions. So one
relationship will be [Jupiter->Pluto] and another will be [Pluto->Jupiter].
To create one-way relationships, I suggest the use of indexes, as in my
previous post.
However, when I followed your link to the example data, I see that there
are connections between some nodes and not others. In that case it would be
preferable to create a mapping of names to nodes, and then as the
relationships are required those nodes can be found easily:
(def create-nodemap [names]
(zipmap names (map convert-to-node names)))
Now you can grab the nodes as needed to work with them:
(defn connect [nodemap name1 name2]
(nrl/create conn (nodemap name1) (nodemap name2 :link)))
(let [nodemap (create-nodemap ["jupiter" "hercules" "neptune" "pluto"])]
(connect nodemap "jupiter" "hercules" :link)
(connect nodemap "jupiter" "neptune" :link)
(connect nodemap "jupiter" "pluto" :link)
(connect nodemap "neptune" "pluto" :link))
I am avoiding many tricks here that I'd use in reality, to avoid making it
too obscure.
Note that the above has links between Juptier, Neptune and Pluto, but
Hercules is only linked to Jupiter. So we don't have everything connected
to everything else. However, this approach is only useful in simple
examples like this, since any real data set would be too large to write
code for every connection. Instead, the actual data (coming from a csv
file, or something) would be read and used to create the connections.
What does your original data look like? Are you just trying to re-create
the graph you linked to, or is the data available in some structured format?
Paul
On Tue, Jun 10, 2014 at 4:08 PM, Francesco Lunelli <
francesco.lune...@gmail.com> wrote:
> Thanks for the answer.
> If I understand well your code it's a partial answer to my question
> because if I'm not wrong it creates a link between to elements at a time.
> What I need is to create all the elements then create on them every kind of
> relation.
> I take as example a graph db used in another engine
> https://raw.githubusercontent.com/wiki/thinkaurelius/titan/images/graph-of-the-gods-2.png
> Here you have a graph of Roman gods, with the name of the gods and the
> links among them. So if I have for example a list of the names of Roman
> gods I need to create all the nodes, then connect them in various mode.
> I want to take the list '("jupiter" "saturn" "hercules" "neptune" "pluto"
> ...) and cycling on it I want to creare the nodes. When I finished to
> create them I need to be able to call every node to crete the various links
> among them. For example I need to link jupiter with pluto, jupiter with
> neptun, neptun with pluto and so on.
>
> Thanks
>
> Francesco
>
>
> On Tuesday, June 10, 2014 7:43:21 PM UTC+2, Paul G wrote:
>
>> Hi Francesco,
>>
>> You want to decouple your code from the data that it is operating on, so
>> your code can operate regardless of the contents of the list. Otherwise,
>> you'll need code that matches the list, in which case it could all be code
>> anyway. Operating on arbitrary lists makes it easy to test simple examples
>> too.
>>
>> A simple way to create links between pages might be like this (assuming
>> that conn is in scope and initialized):
>>
>> (for [list-elt1 the-list, list-elt2 the-list :when (not= list-elt1
>> list-elt2)]
>> (let [page1 (page-fn list-elt1)
>> page2 (page-fn list-elt2)
>> rel (nrl/create conn page1 page2 :links)]
>> ;; do something with rel
>> ))
>>
>> This creates links both ways.
>>
>> If you only want one-way links then the first approach that comes to mind
>> (there are others, and they're probably better) is to index through the seq:
>>
>> (for [n (range (count the-list)), m (range (inc n) (count the-list))]
>> (let [page1 (page-fn (nth the-list n))
>> page2 (page-fn (nth the-list m))
>> rel (nrl/create conn page1 page2 :links)]
>> ;; do something with rel
>> ))
>>
>> The general idea here is to use an arbitrary var to represent your list
>> elements and pages.
>>
>> Does this address your issue?
>>
>> Regards,
>> Paul
>>
>>
>>
>> On Tue, Jun 10, 2014 at 1:04 PM, Francesco Lunelli <francesc...@gmail.com
>> > wrote:
>>
>>> Thanks for the answer, I try to explain better what I have to do.
>>>
>>> I need to create some nodes in Neo4j then I need to create relationships
>>> between those nodes.
>>>
>>> This is an example taken from necons doc.
>>>
>>> (let [conn (nr/connect "http://localhost:7474/db/data/";)
>>> page1 (nn/create conn {:url "http://clojurewerkz.org"})
>>> page2 (nn/create conn {:url "http://clojureneo4j.info"})
>>> ;; a relationship that indicates that page1 links to page2
>>> rel (nrl/create conn page1 page2 :links)]
>>> (println rel)))
>>>
>>> They create two nodes called page1 and pag2 then connect them.
>>>
>>> In my case I have a list of names, I want to create one node for each of
>>> them with the possibility to work on nodes after they are created.
>>> So if I have for example a list like this one (def mylist '(j"john"
>>> "paul" "mary")) I want to create three nodes calling them john paul and
>>> mary storing the value "John" "Paul" "Mary" and after having created them I
>>> want to be albe to connect nodes creating a relationship among them, with a
>>> funciont like rel (nrl/create conn john paul :friend)]
>>>
>>> I hope this example explain better my needs.
>>>
>>> Thanks in advance
>>>
>>> Francesco
>>>
>>>
>>> On Tuesday, June 10, 2014 6:11:16 PM UTC+2, James Reeves wrote:
>>>
>>>> Could you explain a little more what your end goal is?
>>>>
>>>> It sounds like you want a map, but without knowing more about the
>>>> purpose, it's difficult to say.
>>>>
>>>> - James
>>>>
>>>>
>>>> On 10 June 2014 16:43, Francesco Lunelli <francesc...@gmail.com> wrote:
>>>>
>>>>> Hello everybody, I have a newbie question about destructuring and
>>>>> assigning and didn't find an answer in documentation or books.
>>>>>
>>>>> I have a list that contains an arbitrary number of elements for
>>>>> example '("one" "two" "three" ...) I now only that elements are strings.
>>>>>
>>>>> I need to to take every element and use it as the name of a variable
>>>>> inside a let and assign the result of a funcion on that element to that
>>>>> variable.
>>>>> Somthing like this for example:
>>>>>
>>>>> (let [one (clojure.string/capitalize "one")
>>>>> two (clojure.string/capitalize "two")
>>>>> three (clojure.string/capitalize "three")]
>>>>> ;; here I have access to vars one two three etc.
>>>>> )
>>>>>
>>>>> where the names of the vars are taken from the list and values are
>>>>> obtained applying a function on the corresponding element of the list (the
>>>>> capitalize function il only an example, it could be everything else).
>>>>>
>>>>> If I do in this way
>>>>> (for [word ["the" "quick" "brown" "fox"]] (let [word
>>>>> (clojure.string/capitalize word)] (prn word)))
>>>>> it works, but I need to access the variables outside of the cycle for,
>>>>> after having defined and assigned everyone because I need to put in
>>>>> relation some of them.
>>>>>
>>>>> Thanks to everybody
>>>>>
>>>>> Francesco
>>>>>
>>>>>
>>>>>
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